Transmission device and reception device

ABSTRACT

An external device may recognize, in the case of including a communication unit that executes communication via a communication path made up of a pair of differential transmission paths included in a transmission path, information relating to the communication unit thereof. A disk recorder transmits function information indicating that a communication unit (high-speed data line I/F  213 ) configured to execute communication with an external device via a communication path made up of a reserve line and an HPD line of an HDMI cable to a television receiver via a CEC line that is a control data line of the HDMI cable. The television receiver receives function information, whereby whether or not the disk recorder is an eHDMI-compatible device can be determined, and in the case of an eHDMI-compatible device, a compatible transmission format (application) can be recognized.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/451,269 filed Jan. 14, 2010, which is a national phase entry under 35U.S.C. §371 of International Application No. PCT/JP2009/054193 filedMar. 5, 2009, published on Sep. 11, 2009 as WO 2009/110561 A1, whichclaims priority from Japanese Patent Application No. JP 2008-055576filed in the Japanese Patent Office on Mar. 5, 2008, Japanese PatentApplication No. JP2008-136063 filed in the Japanese Patent Office on May23, 2008 and Japanese Patent Application No. JP 2008-208302 filed in theJapanese Patent Office on Aug. 13, 2008.

TECHNICAL FIELD

The present invention relates to a transmission device and a receptiondevice. Specifically, the present invention relates to, in the case ofincluding a communication unit configured to execute communication via acommunication path made up of a pair of differential transmission pathsincluded in a transmission path, a transmission device or the likeconfigured to enable an external device to transmit a signal suitably byallowing the external device to recognize information relating to thecommunication unit thereof.

BACKGROUND ART

In recent years, for example, HDMI (High Definition MultimediaInterface) has come into widespread use as a communication interface fortransmitting digital video signals, i.e., uncompressed (baseband) videosignals (hereafter, referred to as “image data” as appropriate) anddigital audio signals (hereafter, referred to as “audio data” asappropriate) along with the video signal thereof from a DVD (DigitalVersatile Disc) recorder, a set top box, or another AV source (AudioVisual source) to a television receiver, a projector, or anotherdisplay, at high speed. For example, description has been made in PatentDocument 1 regarding the details of the HDMI standard.

Patent Document 1: WO 2002/078336

DISCLOSURE OF INVENTION Technical Problem

With the current HDMI standard, a transmission device (source device)can determine whether or not a reception device (sink device) is aneHDMI-compatible device, according to the voltage state of the reserveline of the HDMI cable. Here, the transmission device or receptiondevice is compatible with eHDMI means that this transmission device orreception device includes a communication unit configured to executecommunication using a communication path made up of predetermined linesof the HDMI cable (e.g., a reserve line and an HPD line).

However, the reception device has difficulty in recognizing whether ornot the transmission device is an eHDMI-compatible device. In the casethat the transmission device is in a busy state, the reception devicehas difficulty in recognizing this busy state. Therefore, receptiondevices have sometimes transmitted an unnecessary signal to atransmission device incompatible with eHDMI, or a transmission devicecompatible with eHDMI in a busy state.

An object of the present invention is to allow a reception device totransmit a signal to a transmission device suitably.

Technical Solution

One concept of the present invention is a transmission devicecomprising:

a video signal transmission unit configured to transmit video signals toan external device via a transmission path with a plurality of channelsusing a differential signal;

a communication unit configured to communicate with the external devicevia a communication path made up of a pair of differential transmissionpaths included in the transmission path;

a function information transmission unit configured to transmit firstfunction information indicating that the transmission device includesthe communication unit to the external device via a control data linemaking up the transmission path; and

a function information reception unit configured to receive secondfunction information indicating that the external device includes acommunication unit configured to execute communication via thecommunication path, which is transmitted from the external device.

Also, another concept of the present invention is a reception devicecomprising:

a video signal reception unit configured to receive video signals froman external device via a transmission path with a plurality of channelsusing a differential signal;

a communication unit configured to communicate with the external devicevia a communication path made up of a pair of differential transmissionpaths included in the transmission path;

a function information transmission unit configured to transmit firstfunction information indicating that the reception device includes thecommunication unit to the external device via a control data line makingup the transmission path; and

a function information reception unit configured to receive secondfunction information indicating that the external device includes acommunication unit configured to execute communication via thecommunication path, which is transmitted from the external device.

With the present invention, the transmission device includes a videosignal transmission unit configured to transmit video signals to anexternal device (reception device) via a transmission path with aplurality of channels using a differential signal, and is, for example,an HDMI source device. The transmission device is provided with acommunication unit configured to communicate with the external devicevia a communication path made up of a pair of differential transmissionpaths included in the transmission path. For example, at least one ofthe pair of differential transmission paths of the communication pathincludes a function for notifying the connection state of the externaldevice using a DC bias potential. For example, the pair of differentialtransmission paths included in the transmission path is a reserve lineand an HPD line making up an HDMI cable.

The function information indicating that the transmission deviceincludes the communication unit is transmitted to the external devicevia the control data line. For example, the control data line is the CECline of the HDMI cable, and the function information is transmitted tothe external device as a CEC signal. This function information mayinclude information of a transmission format (application) that it(transmission device) can support itself.

The reception device includes a video signal reception unit configuredto receive video signals from an external device (transmission device)via a transmission path with a plurality of channels using adifferential signal, and is, for example, an HDMI sink device. Thereception device is provided with a communication unit configured tocommunicate with the external device via a communication path made up ofa pair of differential transmission paths included in the transmissionpath. For example, at least one of the pair of differential transmissionpaths of the communication path includes a function for notifying theconnection state of the external device using a DC bias potential. Forexample, the pair of differential transmission paths included in thetransmission path is a reserve line and an HPD line making up an HDMIcable.

With the reception device, the function information transmitted from theexternal device is received via the control data line. For example, thecontrol data line is the CEC line of the HDMI cable, and the functioninformation is received from the external device as a CEC signal.

The function information indicating that the reception device includesthe communication unit is transmitted to the external device via thecontrol data line. This function information may include the informationof a transmission format (application) that it (reception device) cansupport itself. With the transmission device, the function informationtransmitted from the external device is received via the control dataline.

Thus, in the case that the transmission device includes thecommunication unit, the function information indicating that thetransmission device includes the communication unit is transmitted tothe reception device from the transmission device, and this functioninformation is received at the reception device. Therefore, thereception device can recognize whether or not the external device(transmission device) includes the communication unit, and accordingly,transmitting an unnecessary signal to the external device having nocommunication unit via the communication path can be avoided. Also, inthe case that the function information includes transmission formatinformation that the external device can support, the reception devicecan readily know the transmission format that the external device cansupport from the information thereof.

Also, in the case that the reception device includes the communicationunit, the function information indicating that the reception deviceincludes the communication unit is transmitted to the transmissiondevice from the reception device, and this function information isreceived at the transmission device. Therefore, the transmission devicecan recognize whether or not the external device (reception device)includes the communication unit, and accordingly, transmit anunnecessary signal to the external device having no communication unitvia the communication path can be avoided. Also, in the case that thefunction information includes transmission format information that theexternal device can support, the transmission device can readily knowthe transmission format that the external device can support from theinformation thereof.

With the present invention, for example, an arrangement may be madewherein the reception device includes a transmission requesttransmission unit configured to transmit a transmission request for thefunction information to the external device (transmission device), thetransmission device includes a transmission request reception unitconfigured to receive a transmission request for the functioninformation transmitted from the external device (reception device), andthe function information transmission unit of the transmission devicetransmits the function information to the external device (receptiondevice) when the transmission request reception unit receives thetransmission request. In this case, the reception device can confirmwhether or not the external device includes the communication unit, atarbitrary timing (e.g., at the time of power-on, at the time of inputchange, or the like) by transmitting a transmission request for thefunction information to the external device.

Advantageous Effects

The present invention allows, in the case of including a communicationunit configured to execute communication via a communication path madeup of a pair of differential transmission paths included in atransmission path, the external device to recognize information relatingto the communication unit thereof, and the external device can transmita signal suitably, such as avoiding transmission of unnecessary packets,or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of an AVsystem serving as an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a diskrecorder (source device) making up the AV system.

FIG. 3 is a block diagram illustrating a configuration example of atelevision receiver (sink device) making up the AV system.

FIG. 4 is a block diagram illustrating a configuration example of anHDMI transmission unit (HDMI source) and an HDMI reception unit (HDMIsink).

FIG. 5 is a block diagram illustrating a configuration example of anHDMI transmitter and an HDMI receiver.

FIG. 6 is a diagram illustrating the structure of TMDS transmissiondata.

FIG. 7 is a diagram illustrating the pin array (type A) of an HDMIterminal.

FIG. 8 is a connection diagram illustrating a configuration example of ahigh-speed data line interface of the disk recorder and the televisionreceiver.

FIG. 9 is a connection diagram illustrating a configuration example ofthe high-speed data line interface and the like of the disk recorder andthe television receiver.

FIG. 10 is a diagram illustrating the data structure of AVI InfoFrame.

FIG. 11 is a diagram illustrating the structure of CEC data to betransmitted with a CEC line.

FIG. 12 is a diagram illustrating a structure example of a header block.

FIG. 13 is a diagram illustrating logical addresses to be set accordingto the type of each device with HDMI.

FIG. 14 is a sequence diagram for describing an example of use of an<Exchange Supported Channels Info> message.

FIG. 15 is a diagram illustrating a device configuration example of theAV system.

FIG. 16 is a sequence diagram for describing an example of use of an<Active Supported Channels> message.

FIG. 17 is a sequence diagram for describing an example of use of an<Active Supported Channels> message.

FIG. 18 is a block diagram illustrating a configuration example of theAV system.

FIG. 19 is a diagram for describing an example wherein an HPD signal isset to “H” by changing the voltage of a power supply line without usinga <Request HPD=H> message.

FIG. 20 is a connection diagram illustrating a configuration example ofthe high-speed data line interface and the like of the disk recorder andthe television receiver.

FIG. 21 is a diagram illustrating a voltage change example of the HPDline and a reserve line.

FIG. 22 is a block diagram illustrating a configuration example of thedisk recorder and the television receiver, in the case that functioninformation and compatible transmission format information istransmitted from the disk recorder to the television receiver, and alsocompatible transmission format information is transmitted from thetelevision receiver to the disk recorder.

FIG. 23 is a diagram illustrating a voltage control example of the HPDline with the television receiver (sink device) side, and a voltagecontrol example of the reserve line with the disk recorder (sourcedevice) side and the television receiver (sink device) sidecorresponding thereto.

FIG. 24 is a block diagram illustrating a configuration example of atelevision receiver including multiple, e.g., three HDMI terminals.

FIG. 25 is a diagram illustrating an operation example in the case thatthe sink device is multi-HDMI input.

FIG. 26 is a flowchart illustrating an example of a processing procedureat the time of the CPU of the television receiver (sink device)executing a detection operation as to predetermined HDMI input.

FIG. 27 is a diagram illustrating a voltage change example of the HPDline and the reserve line, in the case that the CPU device of the sinkdevice determines that the source device on the partner side is aneHDMI-incompatible device.

FIG. 28 is a diagram for describing retry processing wherein at the timeof reply from the source device having not arrived even if 100milliseconds elapse, transmission of the function information and thelike is requested as to the source device on the partner side again.

FIG. 29 is a flowchart illustrating an example of the processingprocedure of the CPU of the disk recorder (source device).

FIG. 30 is a block diagram illustrating a configuration example of thedisk recorder and the television receiver, in the case that functioninformation and compatible transmission format information istransmitted from the disk recorder to the television receiver, and alsocompatible transmission format information is transmitted from thetelevision receiver to the disk recorder.

FIG. 31 is a diagram illustrating a voltage control example of thereserve line.

FIG. 32 is a diagram illustrating an operation example in the case thatthe sink device is multi-HDMI input.

FIG. 33 is a flowchart illustrating, in the case of outputting a requestfrom the sink device, an example of the processing procedure of thissink device.

FIG. 34 is a diagram illustrating a voltage change example of thereserve line, in the case that the CPU of the sink device determinesthat the source device on the partner side is an eHDMI-incompatibledevice.

FIG. 35 is a diagram for describing retry processing wherein at the timeof reply from the source device having not arrived even if two secondselapse, transmission of the function information and the like isrequested as to the source device on the partner side again.

FIG. 36 is a flowchart illustrating an example of the processingprocedure of the sink device in the case of outputting a request fromthe source device.

FIG. 37 is a flowchart illustrating an example of the processingprocedure of the sink device in the case of outputting a request fromthe source device.

FIG. 38 is a flowchart illustrating an example of the processingprocedure of the sink device in the case of outputting a request fromthe source device.

FIG. 39 is a block diagram illustrating another configuration example ofthe AV system.

EXPLANATION OF REFERENCE NUMERALS

10 AV system, 11, 12 CDC device, 13 Non-CDC device, 11 a, 11 b, 12 a, 13a HDMI terminal, 14, 15 HDMI cable, 200 AV system, 210 disk recorder,211 HDMI terminal, 212 HDMI transmission unit, 213 high-speed data lineinterface, 250 television receiver, 251 HDMI terminal, 252 HDMIreception unit, 253 high-speed data line interface, 350 HDMI cable, 417SPDIF reception circuit, 449 SPDIF transmission circuit

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings. FIG. 1 illustrates a configurationexample of an AV (Audio Visual) system 200 serving an embodiment. ThisAV system 200 includes a disk recorder 210 serving as a source device,and a television receiver 250 serving as a sink device. With this AVsystem 200, the disk recorder 210 and the television receiver 250 areeHDMI-compatible devices. Here, to be an eHDMI-compatible device meansto include a communication unit configured to execute communicationusing a communication path with a reserve line and an HPD line making upan HDMI cable.

The disk recorder 210 and the television receiver 250 are connected viaan HDMI cable 350. The disk recorder 210 is provided with an HDMIterminal 211 to which an HDMI transmission unit (HDMITX) 212 and ahigh-speed data line interface (I/F) 213 are connected. The televisionreceiver 250 is provided with an HDMI terminal 251 to which an HDMIreception unit (HDMIRX) 252 and a high-speed data line interface (I/F)253 are connected. One end of the HDMI cable 350 is connected to theHDMI terminal 211 of the disk recorder 210, and the other end of thisHDMI cable 350 is connected to the HDMI terminal 251 of the televisionreceiver 250.

With the AV system 200 shown in FIG. 1, the video signals played at thedisk recorder 210 are supplied to the television receiver 250 via theHDMI cable 350, and an image is displayed at this television receiver250. Also, the audio signal played at the disk recorder 210 is suppliedto the television receiver 250 via the HDMI cable 350, and audio isoutput from a speaker of this television receiver 250.

FIG. 2 illustrates a configuration example of the disk recorder 210.This disk recorder 210 includes an HDMI terminal 211, an HDMItransmission unit 212, a high-speed data line interface 213, an antennaterminal 214, a digital tuner 215, a demultiplexer 216, an internal bus217, a recording unit interface 218, a DVD/BD drive 219, an HDD (HardDisk Drive) 220, a CPU (Central Processing Unit) 221, flash ROM (ReadOnly Memory) 222, DRAM (Dynamic Random Access Memory) 223, an Ethernetinterface (Ethernet I/F) 224, a network terminal 225, a DTCP (DigitalTransmission Content Protection) circuit 226, an MPEG decoder 227, agraphics generating circuit 228, a video output terminal 229, and anaudio output terminal 230. Note that “Ethernet” is a registeredtrademark.

The HDMI transmission unit (HDMI source) 212 transmits baseband video(image) and audio data from the HDMI terminal 211 by communicationconforming to HDMI. The details of this HDMI transmission unit 212 willbe described later. The high-speed data line interface 213 is abidirectional communication interface using predetermined lines makingup an HDMI cable (a reserve line and an HPD line in the presentembodiment). The details of this high-speed data line interface 213 willbe described later.

The antenna terminal 214 is a terminal which inputs a televisionbroadcast signal received at a reception antenna (not shown). Thedigital tuner 215 processes the television broadcast signal to be inputto the antenna terminal 214 to output a predetermined transport stream.The demultiplexer 216 extracts a partial TS (Transport Stream) (TSpacket of video data, TS packet of audio data) corresponding to apredetermined selected channel from the transport stream obtained at thedigital tuner 215.

Also, the demultiplexer 216 extracts PSI/SI (Program SpecificInformation/Service Information) from the transport stream obtained atthe digital tuner 215, and outputs this to the CPU 221. With thetransport stream obtained at the digital tuner 215, multiple channelsare multiplexed. Processing for extracting the partial TS of anarbitrary channel from this transport stream can be executed byobtaining the information of the packet ID (PID) of this arbitrarychannel from the PSI/SI (PAT/PMT).

The CPU 221, flash ROM 222, DRAM 223, demultiplexer 216, Ethernetinterface 224, and recording unit interface 218 are connected to theinternal bus 217. The DVD/BD drive 219 and HDD 220 are connected to theinternal bus 217 via the recording unit interface 218. The DVD/BD drive219 and HDD 220 record the partial TS extracted at the demultiplexer216. Also, each of the DVD/BD drive 219 and HDD 220 plays the partial TSrecorded in a recording medium.

The MPEG decoder 227 obtains video data by subjecting a video PES packetmaking up the partial TS extracted at the demultiplexer 216, or playedat the DVD/BD drive 219 or HDD 220 to decode processing. Also, the MPEGdecoder 227 obtains audio data by subjecting an audio PES packet makingup this partial TS to decode processing.

The graphics generating circuit 228 subjects the video data obtained atthe MPEG decoder 227 to graphics data convolution processing or the likeas appropriate. The video output terminal 229 outputs the video dataoutput from the graphics generating circuit 228. The audio outputterminal 230 outputs the audio data obtained at the MPEG decoder 227.

The DTCP circuit 226 encrypts the partial TS extracted at thedemultiplexer 216, or the partial TS played at the DVD/BD drive 219 orHDD 220 as appropriate. Also, the DTCP circuit 226 decrypts theencrypted data supplied from the network terminal 225 or high-speed dataline interface 213 to the Ethernet interface 224.

The CPU 221 controls the operation of each unit of the disk recorder210. The flash ROM 222 executes storing of control software, and storingof data. The DRAM 223 makes up a work area of the CPU 221. The CPU 221renders the software and data read out from the flash ROM 222 onto theDRAM 223, activates the software to control each unit of the diskrecorder 210.

The operation of the disk recorder 210 shown in FIG. 2 will be describedbriefly.

The television broadcast signal input to the antenna terminal 214 issupplied to the digital tuner 215. With this digital tuner 215, thetelevision broadcast signal is subjected to processing to extract apredetermined transport stream, and this predetermined transport streamis supplied to the demultiplexer 216. With the demultiplexer 216, thepartial TS (TS packet of video data, TS packet of audio data)corresponding to a predetermined channel is extracted from the transportstream. This partial TS is supplied to the DVD/BD drive 219 or HDD 220via the recording unit interface 218, and is recorded therein based on arecording instruction from the CPU 221.

Also, as described above, the partial TS extracted at the demultiplexer216, or the partial TS played at the DVD/BD drive 219 or HDD 220 issupplied to the MPEG decoder 227. With this MPEG decoder 227, the videoPES packet made up of a TS packet of video data is subjected to decodeprocessing, and video data is obtained. This video data is subjected tographics data convolution processing or the like at the graphicsgenerating circuit 228, and is then output to the video output terminal229. Also, with the MPEG decoder 227, the audio PES packet made up of aTS packet of audio data is subjected to decode processing, and audiodata is obtained. This audio data is output to the audio output terminal230.

The video (image) data and audio data obtained at the MPEG decoder 227corresponding to the partial TS played at the DVD/BD drive 219 or HDD220 is supplied to the HDMI transmission unit 212, and is transmitted toan HDMI cable connected to the HDMI terminal 211.

With the high-speed data line interface 213, an IP packet including aremote control code transmitted via the predetermined lines of the HDMIcable connected to the HDMI terminal 211 is received. This IP packet issupplied to the CPU 221 via the Ethernet interface 224. In the case thatthe remote control code included in this IP packet relates to thecontrol of the disk recorder 210, the CPU 221 controls each unit of thedisk recorder 210 based on this remote control code.

Also, in the event that the partial TS extracted at the demultiplexer216, or the partial TS played at the DVD/BD drive 219 or HDD 220 istransmitted to a network, this partial TS is encrypted at the DTCPcircuit 226, and is then output to the network terminal 225 via theEthernet interface 224.

FIG. 3 illustrates a configuration example of the television receiver250. This television receiver 250 includes an HDMI terminal 251, an HDMIreception unit 252, a high-speed data line interface 253, an antennaterminal 257, a digital tuner 258, a demultiplexer 259, an MPEG (MovingPicture Expert Group) decoder 260, a video/graphics processing unit 261,a panel driving circuit 262, a display panel 263, an audio signalprocessing circuit 264, an audio amplifying circuit 265, a speaker 266,a DTCP circuit 267, an internal bus 270, a CPU 271, flash ROM 272, DRAM273, an Ethernet interface (Ethernet I/F) 274, a network terminal 275, aremote control reception unit 276, and a remote control transceiver 277.

The antenna terminal 257 is a terminal for inputting the televisionsignal received at a reception antenna (not shown). The digital tuner258 subjects the television broadcast signal input to the antennaterminal 257 to processing, and outputs the predetermined transportstream corresponding to the channel selected by the user. Thedemultiplexer 259 extracts the partial TS (Transport Stream) (TS packetof video data, TS packet of audio data) corresponding to the channelselected by the user from the transport stream obtained at the digitaltuner 258.

Also, the demultiplexer 259 extracts PSI/SI (Program SpecificInformation/Service Information) from the transport stream obtained atthe digital tuner 258, and outputs this to the CPU 271. With thetransport stream obtained at the digital tuner 258, multiple channelsare multiplexed. The processing for extracting the partial TS of anarbitrary channel from this transport stream at the demultiplexer 259can be executed by obtaining the information of the packet ID (PID) ofthis arbitrary channel from the PSI/SI (PAT/PMT).

The MPEG decoder 260 subjects the video PES (Packetized ElementaryStream) packet made up of the TS packets of the video data obtained atthe demultiplexer 259 to decode processing, thereby obtaining videodata. Also, the MPEG decoder 260 subjects the audio PES packet made upof the TS packets of the audio data obtained at the demultiplexer 259,thereby obtaining audio data. Note that this MPEG decoder 260 subjectsthe video and audio PES packets obtained by being decrypted at the DTCPcircuit 267 to decode processing as appropriate, thereby obtaining videodata and audio data.

The video/graphics processing circuit 261 subjects the video dataobtained at the MPEG decoder 260 to multi screen processing, graphicsdata convolution processing, or the like as appropriate. The paneldriving circuit 262 drives the display panel 263 based on the video dataoutput from the video/graphics processing circuit 261. The display panel263 is configured of, for example, an LCD (Liquid Crystal Display), PDP(Plasma Display Panel), or the like. The audio signal processing circuit264 subjects the audio data obtained at the MPEG decoder 260 tonecessary processing such as D/A conversion or the like. The audioamplifying circuit 265 amplifies the audio signal output from the audiosignal processing circuit 264, and supplies this to the speaker 266.

The DTCP circuit 267 encrypts the partial TS extracted at thedemultiplexer 259 as appropriate. Also, the DTCP circuit 267 decryptsthe encrypted data supplied from the network terminal 275 or high-speeddata line interface 253 and 256 to the Ethernet interface 274.

The CPU 271 controls the operation of each unit of the televisionreceiver 250. The flash ROM 272 executes storing of control software,and storing of data. The DRAM 273 makes up a work area of the CPU 271.The CPU 271 renders the software and data read out from the flash ROM272 onto the DRAM 273, activates the software to control each unit ofthe television receiver 250. The remote control reception unit 276receives the remote control signal (remote control code) transmittedfrom the remote control transceiver 277, and supplies this to the CPU271. The CPU 271, flash ROM 272, DRAM 273, and Ethernet interface 274are connected to the internal bus 270.

The HDMI reception unit (HDMI sink) 252 receives baseband video (image)and audio data supplied to the HDMI terminal 251 by communicationconforming to HDMI. The details of this HDMI reception unit 252 will bedescribed later. The high-speed data line interface 253 is abidirectional communication interface using predetermined lines makingup an HDMI cable (a reserve line and an HPD line in the presentembodiment). The details of this high-speed data line interface 253 willbe described later.

The operation of the television receiver 250 shown in FIG. 3 will bedescribed briefly.

The television broadcast signal input to the antenna terminal 157 issupplied to the digital tuner 258. With this digital tuner 258, thetelevision broadcast signal is subjected to processing, thepredetermined transport stream corresponding to the channel selected bythe user is output, and this predetermined transport stream is suppliedto the demultiplexer 259. With this demultiplexer 259, the partial TS(TS packet of video data, TS packet of audio data) corresponding to thechannel selected by the user is extracted from the transport stream, andthis partial TS is supplied to the MPEG decoder 260.

With the MPEG decoder 260, the video PES packet made up of a TS packetof video data is subjected to decode processing, thereby obtaining videodata. This video data is subjected to multi screen processing, graphicsdata convolution processing, or the like at the video/graphicsprocessing circuit 261 as appropriate, and is then supplied to the paneldriving circuit 262. Therefore, the image corresponding to the channelselected by the user is displayed on the display panel 263.

Also, with the MPEG decoder 260, the audio PES packet made up of a TSpacket of audio data is subjected to decode processing, therebyobtaining audio data. This audio data is subjected to necessaryprocessing such as D/A conversion or the like at the audio signalprocessing circuit 264, and further, is amplified at the audioamplifying circuit 265, and is then supplied to the speaker 266.Therefore, the audio corresponding to the channel selected by the useris output from the speaker 266.

In the event that the partial TS extracted at the demultiplexer 259 istransmitted to a network at the time of receiving the above televisionbroadcast signal, this partial TS is encrypted at the DTCP circuit 267,and is then output to the network terminal 275 via the Ethernetinterface 274.

With the remote control reception unit 276, the remote control code(remote control signal) transmitted from the remote control transceiver277 is received, and this remote control code is supplied to the CPU271. In the case that the remote control code relates to the control ofthe television receiver 250, the CPU 271 controls each unit of thetelevision receiver 250 based on this remote control code.

Also, with the CPU 271, an IP packet including the remote control codesupplied from the remote control reception unit 276 is generated. ThisIP packet is output to the HDMI terminal 251 via the Ethernet interface274 and high-speed line interface 253.

Also, this IP packet is transmitted to the network as appropriate. Inthis case, this IP packet is output to the network terminal 275 via theEthernet interface 274. Also, this IP packet is output to the HDMIterminal 251 via the Ethernet interface 274 and high-speed data lineinterface 253.

Note that the encrypted partial TS supplied from the network terminal275 to the Ethernet interface 274, or supplied from the HDMI terminal251 to the Ethernet interface 274 via the high-speed data line interface253, is decrypted at the DTCP circuit 267, and is then supplied to theMPEG decoder 260. Hereafter, the operation of the television receiver250 is the same operation as at the time of receiving the abovetelevision broadcast signal, where an image is displayed on the displaypanel 263, and audio is output from the speaker 266.

Also, with the HDMI reception unit 252, the video (image) data and audiodata input to the HDMI terminal 251 via the HDMI cable is obtained. Thisvideo data and audio data is each supplied to the video/graphicsprocessing circuit 261 and the audio signal processing circuit 264.Hereafter, the operation of the television receiver 250 is the sameoperation as at the time of receiving the above television broadcastsignal, where an image is displayed on the display panel 263, and audiois output from the speaker 266.

FIG. 4 illustrates a configuration example of the HDMI transmission unit(HDMI source) 212 of the disk recorder 210, and the HDMI reception unit(HDMI sink) 252 of the television receiver 250 with the AV system 200 inFIG. 1.

The HDMI source 212 transmits the differential signals corresponding tothe pixel data of uncompressed one screen worth of image to the HDMIsink 252 in one direction using multiple channels during a valid imagesection wherein a horizontal retrace line section and a vertical retraceline section are removed from a section from a vertical synchronizingsignal to the next vertical synchronizing signal (hereafter, alsoreferred to as “active video section” as appropriate), and alsotransmits the differential signals corresponding to at least audio dataalong with the image, control data, other auxiliary data, and the likealong with the image to the HDMI sink 252 in one direction usingmultiple channels during a horizontal retrace line section and avertical retrace line section.

That is to say, the HDMI source 212 includes a transmitter 81. Thetransmitter 81 converts, for example, the pixel data of an uncompressedimage to the corresponding differential signals, and serially transmitsthese to the HDMI sink 252 connected thereto via the HDMI cable 350 inone direction using three TMDS channels #0, #1, and #2, which aremultiple channels.

Also, the transmitter 81 converts audio data along with an uncompressedimage, and further, necessary control data, other auxiliary data, andthe like into the corresponding differential signals, and seriallytransmits these to the HDMI sink 252 connected thereto via the HDMIcable 350 in one direction using the three TMDS channels #0, #1, and #2.

Further, the transmitter 81 transmits the pixel clock synchronized withthe pixel data to be transmitted using the three TMDS channels #0, #1,and #0 to the HDMI sink 252 connected thereto via the HDMI cable 350using a TMDS clock channel. Here, with one of the TMDS channel #i (i=0,1, 2), the pixel data of 10 bits is transmitted during one clock of thepixel clock.

The HDMI sink 252 receives the differential signals corresponding topixel data, transmitted from the HDMI source 212 in one direction usingmultiple channels during an active video section, and also receives thedifferential signals corresponding to audio data and control data,transmitted from the HDMI source 212 in one direction during ahorizontal retrace line section and a vertical retrace line section.

That is to say, the HDMI sink 252 includes a receiver 82. The receiver82 receives the differential signals corresponding to pixel data,transmitted in one direction from the HDMI source 212 connected theretovia the HDMI cable 350 using the TMDS channels #0, #1, and #2, in syncwith the pixel clock transmitted similarly from the HDM source 212 usingthe TMDS clock channel.

The transmission channels of the HDMI system made up of the HDMI source212 and the HDMI sink 252 include, in addition to the three TMDSchannels #0 through #2 serving as transmission channels for seriallytransmitting pixel data and audio data in one direction in sync with thepixel clock, and the TMDS clock channel serving as a transmissionchannel for transmitting the pixel clock, transmission channels referredto as a DDC (Display Data Channel) 83 and a CEC line 84.

The DDC 83 is made up of two unshown signal lines included in the HDMIcable 350, and is used for the HDMI source 212 reading out E-EDID(Enhanced Extended Display Identification Data) from the HDMI sink 252connected thereto via the HDMI cable 350.

That is to say, the HDMI sink 252 includes, in addition to the HDMIreceiver 81, EDID ROM (Read Only Memory) 85 which stores E-EDID that isperformance information relating to the performance(configuration/capability) of itself. The HDMI source 212 reads out theE-EDID of this HDMI sink 252 from the HDMI sink 252 connected theretovia the HDMI cable 350, via the DDC 83, and recognizes the settings ofthe performance of the HDMI sink 252, i.e., for example, the format(profile) of the image corresponding to the electronic equipmentincluding the HDMI sink 252, for example, RGB, YCbCr4:4:4, YCbCr4:2:2,or the like.

The CEC line 84 is made up of a single signal line not shown included inthe HDMI cable 350, and is used for executing the bidirectionalcommunication of data for control between the HDMI source 212 and theHDMI sink 252.

Also, the HDMI cable 350 includes a line (HPD line) 86 connected to apin called HPD (Hot Plug Detect). A source device uses this line 86,whereby connection of a sink device can be detected. Also, the HDMIcable 350 includes a line 87 used for supplying power from a sourcedevice to a sink device. Further, the HDMI cable 351 includes a reserveline 88.

FIG. 5 illustrates a configuration example of the HDMI transmitter 81and the HDMI receiver 82 in FIG. 4.

The transmitter 81 includes three encoders/serializers 81A, 81B, and 81Ccorresponding to the three TMDS channels #0, #1, and #2, respectively.Each of the encoders/serializers 81A, 81B, and 81C encodes image data,auxiliary data, and control data supplied thereto, converts this fromparallel data to serial data, and transmits this using a differentialsignal. Here, in the case that the image data includes, for example,three components of R (Red), G (Green), and B (Blue), the B component issupplied to the encoder/serializer 81A, the G component is supplied tothe encoder/serializer 81B, and R component is supplied to theencoder/serializer 81C.

Also, examples of the auxiliary data include audio data and controlpacket, the control packet is supplied to, for example, theencoder/serializer 81A, and the audio data is supplied to theencoders/serializers 81B and 81C.

Further, examples of the control data include a 1-bit verticalsynchronizing signal (VSYNC), a 1-bit horizontal synchronizing signal(HSYNC), and 1-bit control bits CTL0, CTL1, CTL2, and CTL3. The verticalsynchronizing signal and the horizontal synchronizing signal aresupplied to the encoder/serializer 81A. The control bits CTL0 and CTL 1are supplied to the encoder/serializer 81B, and the control bits CTL2and CTL 3 are supplied to the encoder/serializer 81C.

The encoder/serializer 81A transmits the B component of image data,vertical synchronizing signal and horizontal synchronizing signal, andauxiliary data supplied thereto, in a time-sharing manner. That is tosay, the encoder/serializer 81A takes the B component of image datasupplied thereto as parallel data in increments of 8 bits that are thenumber of fixed bits. Further, the encoder/serializer 81A encodes theparallel data thereof to convert this into serial data, and transmitsthis using the TMDS channel #0.

Also, the encoder/serializer 81A encodes the 2-bit parallel data of avertical synchronizing signal and a horizontal signal supplied theretoto convert this into serial data, and transmits this using the TMDSchannel #0. Further, the encoder/serializer 81A takes the auxiliary datasupplied thereto as parallel data in increments of 4 bits. Further, theencoder/serializer 81A encodes the parallel data thereof to convert thisinto serial data, and transmits this using the TMDS channel #0.

The encoder/serializer 81B transmits the G component of image datasupplied thereto, control bits CTL0 and CTL1, and auxiliary datasupplied thereto in a time-sharing manner. That is to say, theencoder/serializer 81B takes the G component of image data suppliedthereto as parallel data in increments of 8 bits, this being the numberof fixed bits. Further, the encoder/serializer 81B encodes the paralleldata thereof to convert this into serial data, and transmits this usingthe TMDS channel #1.

Also, the encoder/serializer 81B encodes the 2-bit parallel data of thecontrol bits CTL0 and CTL1 supplied thereto to convert this into serialdata, and transmits this using the TMDS channel #1. Further, theencoder/serializer 81B takes the auxiliary data supplied thereto asparallel data in increments of 4 bits. The encoder/serializer 81Bencodes the parallel data thereof to convert this into serial data, andtransmits this using the TMDS channel #1.

The encoder/serializer 81C transmits the R component of image data,control bits CTL2 and CTL3, and auxiliary data supplied thereto in atime-sharing manner. That is to say, the encoder/serializer 81C takesthe R component of image data supplied thereto as parallel data inincrements of 8 bits, this being the number of fixed bits. Further, theencoder/serializer 81C encodes the parallel data thereof to convert thisinto serial data, and transmits this using the TMDS channel #2.

Also, the encoder/serializer 81C encodes the 2-bit parallel data of thecontrol bits CTL2 and CTL3 supplied thereto to convert this into serialdata, and transmits this using the TMDS channel #2. Further, theencoder/serializer 81C takes the auxiliary data supplied thereto asparallel data in increments of 4 bits. The encoder/serializer 81Cencodes the parallel data thereof to convert this into serial data, andtransmits this using the TMDS channel #2.

The receiver 82 includes three recoveries/decoders 82A, 82B, and 82Ccorresponding to the three TMDS channels #0, #1, and #2, respectively.Each of the recoveries/decoders 82A, 82B, and 82C receive image data,auxiliary data, and control data transmitted using differential signalswith the TMDS channels #0, #1, and #2. Further, each of therecoveries/decoders 82A, 82B, and 82C converts the image data, auxiliarydata, and control data from serial data to parallel data, furtherdecodes this, and outputs this.

That is to say, the recovery/decoder 82A receives the B component ofimage data, vertical synchronizing signal and horizontal synchronizingsignal, and auxiliary data transmitted using differential signals withthe TMDS channel #0. Subsequently, the recovery/decoder 82A converts theB component of the image data, vertical signal and horizontal signal,and auxiliary data from serial data to parallel data, decodes this, andoutputs this.

The recovery/decoder 82B receives the G component of image data, controlbits CTL0 and CTL1, and auxiliary data transmitted using differentialsignals with the TMDS channel #1. Subsequently, the recovery/decoder 82Bconverts the G component of the image data, control bits CTL0 and CTL1,and auxiliary data thereof from serial data to parallel data, decodesthis, and outputs this.

The recovery/decoder 82C receives the R component of image data, controlbits CTL2 and CTL3, and auxiliary data transmitted using differentialsignals with the TMDS channel #2. Subsequently, the recovery/decoder 82Cconverts the R component of the image data, control bits CTL2 and CTL3,and auxiliary data thereof from serial data to parallel data, decodesthis, and outputs this.

FIG. 6 illustrates an example of a transmission section (period) whereinvarious types of transmission data are transmitted using the three TMDSchannels #0, #1, and #2 of HDMI. Note that FIG. 6 illustrates thesections of various types of transmission data in the case that aprogressive image of which the vertical×width is 720×480 pixels istransmitted with the TMDS channels #0, #1, and #2.

With a video field where transmission data is transmitted with the threeTMDS channels #0, #1, and #2 of HDMI, there are three types of sectionsaccording to the type of transmission data; video data section (VideoData period), data island section (Data Island period), and controlsection (Control period).

Here, the video field section is a section from the leading edge (activeedge) of a certain vertical synchronizing signal to the leading edge ofthe next vertical synchronizing signal, and is divided into a horizontalblanking period (horizontal blanking), a vertical blanking period(vertical blanking), and an active video section (Active Video) which isthe video field section from which the horizontal blanking period andthe vertical blanking period are removed.

The video data section is assigned to the active video section. Duringthis video data section, the data of 720 pixels×480 lines worth of validpixels (Active pixel) making up one screen worth of uncompressed imagedata is transmitted.

The data island section and the control section are assigned to thehorizontal blanking period and the vertical blanking period. During thisdata island section and the control section, auxiliary data (Auxiliarydata) is transmitted.

That is to say, the data island section is assigned to a portion of thehorizontal blanking period and the vertical blanking period. During thisdata island section, of the auxiliary data, data not relating tocontrol, e.g., a packet of audio data or the like is transmitted.

The control section is assigned to another portion of the horizontalblanking period and the vertical blanking period. During this controlsection, of the auxiliary data, data relating to control, e.g., thevertical synchronizing signal and horizontal synchronizing signal,control packet, or the like is transmitted.

Here, with the current HDMI, the frequency of the pixel clocktransmitted with the TMDS clock channel is, for example, 165 MHz, and inthis case, the transmission rate of the data island section isapproximately 500 Mbps.

FIG. 7 illustrates the pin arrays of the HDMI terminals 211 and 251.These pin arrays are called type A (type-A).

Two lines which are differential lines where TMDS Data #i+ and TMDS Data#i− serving as the differential signals of the TMDS channel #i areconnected to pins to which the TMDS Data #i+ is assigned (pins of whichthe pin numbers are 1,4, and 7), and pins to which the TMDS Data #i− isassigned (pins of which the pin numbers are 3,6, and 9).

Also, the CEC line 84, where the CEC signal which is data for control istransmitted, is connected to a pin of which the pin number is 13, and apin of which the pin number is 14 is an empty (reserved) pin. Also, aline where an SDA (Serial Data) signal such as an E-EDID signal or thelike is transmitted is connected to a pin of which the pin number is 16,and a line where an SCL (Serial Clock) signal that is a clock signalused for synchronization at the time of transmission/reception of theSDA signal is transmitted is connected to a pin of which the pin numberis 15. The above DDC 83 is made up of a line where the SDA signal istransmitted, and a line where the SCL signal is transmitted.

Also, an HPD line 86 used for a source device detecting connection of asink device as described above is connected to a pin of which the pinnumber is 19. Also, a line 87 used for supplying power as describedabove is connected to a pin of which the pin number is 18.

FIG. 8 illustrates a configuration example of the high-speed data lineinterface 213 of the disk recorder 210, and the high-speed data lineinterface 253 of the television receiver 250. These interface 213 and253 make up a communication unit configured to execute LAN (Local AreaNetwork) communication. This communication unit executes bidirectionalcommunication using, of the multiple lines making up the HDMI cable 350,a pair of differential lines, and with the present embodiment, a reserveline (Ether-line) corresponding to an empty (reserve) pin (pin 14), andan HPD line (Ether+ line) corresponding to the HPD pin (pin 19).

The disk recorder 210 includes a LAN signal transmission circuit 411, aterminating resistor 412, an AC coupling capacitances 413 and 414, a LANsignal reception circuit 415, and a subtraction circuit 416, which makeup the high-speed data line interface 213.

A series circuit of the AC coupling capacitance 413, terminatingresistor 412, and AC coupling capacitance 414 is connected between thepin 14 and pin 19 of the HDMI terminal 211. A mutual connection point P1of the AC coupling capacitance 413 and the terminating resistor 412 isconnected to the positive output side of the LAN signal transmissioncircuit 411, and is also connected to the positive input side of the LANsignal reception circuit 415. Also, a mutual connection point P2 of theAC coupling capacitance 414 and the terminating resistor 412 isconnected to the negative output side of the LAN signal transmissioncircuit 411, and is also connected to the negative input side of the LANsignal reception circuit 415. The input side of the LAN signaltransmission circuit 411 is supplied with a transmission signal(transmission data) SG411.

Also, the positive side terminal of the subtraction circuit 416 issupplied with the output signal SG412 of the LAN signal receptioncircuit 415, and the negative side terminal of this subtraction circuit416 is supplied with a transmission signal (transmission data) SG411.With this subtraction circuit 416, the transmission signal SG411 issubtracted from the output signal SG412 of the LAN signal receptioncircuit 415, and a reception signal (reception data) SG413 is obtained.

The television receiver 250 includes a LAN signal transmission circuit441, a terminating resistor 442, an AC coupling capacitances 443 and444, a LAN signal reception circuit 445, and a subtraction circuit 446,which make up the high-speed data line interface 253. Also, thetelevision receiver 250 includes pull-up resistors 447 and 448.

A series circuit of the AC coupling capacitance 443, terminatingresistor 442, and AC coupling capacitance 444 is connected between thepin 14 and pin 19 of the HDMI terminal 251. A mutual connection point P3of the AC coupling capacitance 443 and the terminating resistor 442 isconnected to the positive output side of the LAN signal transmissioncircuit 441, and is also connected to the positive input side of the LANsignal reception circuit 445. Also, a mutual connection point P4 of theAC coupling capacitance 444 and the terminating resistor 442 isconnected to the negative output side of the LAN signal transmissioncircuit 441, and is also connected to the negative input side of the LANsignal reception circuit 445. The input side of the LAN signaltransmission circuit 441 is supplied with a transmission signal(transmission data) SG417.

Also, the positive side terminal of the subtraction circuit 446 issupplied with the output signal SG418 of the LAN signal receptioncircuit 445, and the negative side terminal of this subtraction circuit446 is supplied with a transmission signal (transmission data) SG417.With this subtraction circuit 446, the transmission signal SG417 issubtracted from the output signal SG418 of the LAN signal receptioncircuit 445, and a reception signal (reception data) SG419 is obtained.

The pin 19 of the HDMI terminal 251 is connected to a power supply line(+5.0V) via a pull-up resistor 447. Also, this television receiver 250is an eHDMI-compatible device, and accordingly, the pin 14 of the HDMIterminal 251 is connected to the power supply line (+5.0V) via thepull-up resistor 448.

A reserve line 501 and an HPD line 502 included in the HDMI cable 350make up a differential twist pair. The source side edge 511 of thereserve line 501 is connected to the 14 pin of the HDMI terminal 211,and the sink side edge 521 of this reserve line 501 is connected to the14 pin of the HDMI terminal 251. Also, the source side edge 512 of theHPD line 502 is connected to the 19 pin of the HDMI terminal 211, andthe sink side edge 522 of this HPD line 502 is connected to the 19 pinof the HDMI terminal 251.

Next, the operation of LAN communication with the high-speed data lineinterfaces 213 and 253 configured as described above will be described.

With the disk recorder 210, the transmission signal (transmission data)SG411 is supplied to the input side of the LAN signal transmissioncircuit 411, and the differential signals corresponding to thetransmission signal SG411 (positive output signal, negative outputsignal) are output from this LAN signal transmission circuit 411.Subsequently, the differential signals output from the LAN signaltransmission circuit 411 are supplied to the connection points P1 andP2, and are transmitted to the television receiver 250 via the pair lineof the HDMI cable 350 (reserve line 501, HPD line 502).

Also, with the television receiver 250, the transmission signal(transmission data) SG417 is supplied to the input side of the LANsignal transmission circuit 441, and the differential signalscorresponding to the transmission signal SG417 (positive output signal,negative output signal) are output from this LAN signal transmissioncircuit 441. Subsequently, the differential signals output from the LANsignal transmission circuit 441 are supplied to the connection points P3and P4, and are transmitted to the disk recorder 210 via the pair lineof the HDMI cable 350 (reserve line 501, HPD line 502).

Also, with the disk recorder 210, the input side of the LAN signalreception circuit 415 is connected to the connection points P1 and P2,and accordingly, an addition signal is obtained from the transmissionsignal corresponding to the differential signal (current signal) outputfrom the LAN signal transmission circuit 411, and the reception signalcorresponding to the differential signal to be transmitted from thetelevision receiver 250 as described above, as the output signal SG412of this LAN signal reception circuit 415. With the subtraction circuit416, the transmission signal SG411 is subtracted from the output signalSG412 of the LAN signal reception circuit 415. Therefore, the outputsignal SG413 of this subtraction circuit 416 corresponds to thetransmission signal (transmission data) SG417 of the television receiver250.

Also, with the television receiver 250, the input side of the LAN signalreception circuit 445 is connected to the connection points P3 and P4,and accordingly, an addition signal is obtained from the transmissionsignal corresponding to the differential signal (current signal) outputfrom the LAN signal transmission circuit 441, and the reception signalcorresponding to the differential signal to be transmitted from the diskrecorder 210 as described above, as the output signal SG418 of this LANsignal reception circuit 445. With the subtraction circuit 446, thetransmission signal SG417 is subtracted from the output signal SG418 ofthe LAN signal reception circuit 445. Therefore, the output signal SG419of this subtraction circuit 446 corresponds to the transmission signal(transmission data) SG411 of the disk recorder 210.

Thus, bidirectional LAN communication can be executed between thehigh-speed data line interface 213 of the disk recorder 210, and thehigh-speed data line interface 253 of the television receiver 250.

Note that, with the television receiver 250, the pin 19 of the HDMIterminal 251 is connected to the power supply line (+5.0V). Therefore,when the television receiver 250 is connected to the disk recorder 210via the HDMI cable 350, the voltage Vhpd at the pin 19 of the HDMIterminal 211 increases. Accordingly, with the disk recorder 210, whetheror not the television receiver 250 has been connected to the diskrecorder 210 via the HDMI cable 350 can be detected by monitoring thevoltage Vrsv at the pin 19 of the HDMI terminal 211.

Also, with the television receiver 250, the pin 14 of the HDMI terminal251 is connected to the power supply line (+5.0V). Therefore, when thetelevision receiver 250 is connected to the disk recorder 210 via theHDMI cable 350, the voltage Vhpd at the pin 14 of the HDMI terminal 211increases. Accordingly, with the disk recorder 210, whether or not thetelevision receiver 250 is an eHDMI-compatible device can be recognizedby monitoring the voltage Vhpd at the pin 14 of the HDMI terminal 211.

With the present embodiment, the television receiver 250 can recognizethat the disk recorder 210 is an eHDMI-compatible device. The techniquethereof will be described below.

For example, when the television receiver 250 is connected to the diskrecorder 210 via the HDMI cable 350, the disk recorder 210 transmitsfunction information indicating that it itself is an eHDMI-compatibledevice, i.e., includes a communication unit (high-speed data lineinterface 213 or the like) using a communication path made up of thereserve line and the HPD line of the HDMI cable 350, to the televisionreceiver 250. Also, the disk recorder 210 includes transmission format(application) information that the disk recorder 210 can support in thisfunction information.

Here, the transmission format information is information regardingwhether supporting only the SPDIF (Sony Philips Digital InterFace)signal, or supporting only the Ethernet signal, or supporting both ofthe SPDIF signal and the Ethernet signal.

Now, the SPDIF signal will be described briefly. This SPDIF signal is asignal to be transmitted with the SPDIF standard. The SPDIF standard isan interface standard used for transmitting digital audio signals inreal time. The SPDIF signal is subjected to biphase mark modulation, andaccordingly, includes a clock component within the signal thereof.

Note that the configuration example of the above FIG. 8 illustrates thecase where only the Ethernet signal is supported. In the case of alsosupporting the SPDIF signal, the configuration example thereof is suchas shown in FIG. 9. The television receiver 250 includes a SPDIFtransmission circuit 449. The SPDIF signal output from this SPDIFtransmission circuit 449 is transmitted to the disk recorder 210 sidewith the same phase by adders 451 and 452 using the reserve line and theHPD line making up the HDMI cable 350. Here, the SPDIF transmissioncircuit 449 makes up, in the same way as with the high-speed data lineinterface 253, a communication unit configured to execute communicationusing a communication path made up of the reserve line and the HPD line.

Also, the disk recorder 210 includes a SPDIF reception circuit 417. TheSPDIF signal transmitted with the same phase from the televisionreceiver 250 side with the reserve line and the HPD line making up theHDMI cable 350 is added at the adder 421, and is supplied to the SPDIFreception circuit 417. Here, the SPDIF reception circuit 417 makes up,in the same way as with the high-speed data line interface 213, acommunication unit configured to execute communication using acommunication path made up of the reserve line and the HPD line.

Note that, in the case of supporting only the SPDIF signal, with theconfiguration example shown in FIG. 9, the configuration is changed byremoving the high-speed data interfaces 213 and 253 therefrom.

For example, the disk recorder 210 inserts the above functioninformation during the blanking period of the video signal to betransmitted to the television receiver 250 with the above TMDS channel,thereby transmitting this function information to the televisionreceiver 250. Here, the disk recorder 210 uses, for example, the AVI(Auxiliary Video Information) InfoFrame packet of the HDMI to insert theabove function information during the blanking period of the videosignal.

This AVI InfoFrame packet is disposed during the above data islandsection. FIG. 10 illustrates the data structure of the AVI InfoFramepacket. With HDMI, according to this AVI InfoFrame packet, auxiliaryinformation relating to an image can be transmitted from a source deviceto a sink device.

With the present embodiment, the function information is disposed, suchas shown in the data structure of the AVI InfoFrame in FIG. 10, in onebit of E1 at the fourth byte (Data Byte 1), and two bits of E2 and E3 atthe eighth byte (Data Byte 5) in a hierarchical manner. E1 that is 1-bitdata is data for identifying whether or not an eHDMI-compatible deviceincluding a communication unit (high-speed data line interface 213,SPDIF reception circuit 417) configured to execute communication via acommunication path made up of the reserve line and the HPD line of theHDMI cable 350. Here, when E1=0, this indicates not beingeHDMI-compatible, and when E1=1, this indicates being eHDMI-compatible.

Also, E2 and E3 that are 2-bit data are bit data for identifying whethersupporting only the SPDIF signal, supporting only the Ethernet signal,or supporting both the SPDIF signal and the Ethernet signal. Forexample, when E2=1, and E3=0, this indicates supporting only the SPDIFsignal, and when E2=0, and E3=1, this indicates supporting only theEthernet signal, and when E2=1, and E3=1, this indicates supporting bothof the SPDIF signal and the Ethernet signal.

In the case that the disk recorder 210 inserts the function informationduring the blanking period of the video signal to be transmitted to thetelevision receiver 250 with the TMDS channel as described above,thereby transmitting this function information to the televisionreceiver 250, the television receiver 250 receives this functioninformation by extracting the above function information from theblanking period of the video signal received from the disk recorder 210with the TMDS channel.

Note that the above description has shown the case where the functioninformation is inserted during the blanking period of a video signalusing the AV InfoFrame packet. Though detailed description will beomitted, the function information may be inserted during the blankingperiod of a video signal even using other packets such as a GCP packetor the like.

Also, for example, the disk recorder 210 transmits the above functioninformation to the television receiver 250 via the CEC line 84 which isthe control data line of the HDMI cable 350. In this case, thetelevision receiver 250 receives the function information from the diskrecorder 210 via the CEC line 84.

The television receiver 250 receives the function information asdescribed above, whereby whether or not the disk recorder 210 is aneHDMI-compatible device can be recognized, and in the case of aneHDMI-compatible device, the transmission format (application) that thedisk recorder 210 can support can be recognized. Note that, as describedabove, in the case that the function information is transmitted from thedisk recorder 210 to the television receiver 250, the HDMI transmissionunit 212 of the disk recorder 210 makes up a function informationtransmission unit, and the HDMI reception unit 252 of the televisionreceiver 250 makes up a function information reception unit.

Note that the above description has shown the case where the televisionreceiver 250 is connected to the disk recorder 210 via the HDMI cable350, the disk recorder 210 automatically transmits the functioninformation to the television receiver 250. However, an arrangement maybe made wherein a transmission request for this function information istransmitted from the television receiver 250 side to the disk recorder210, and when receiving this transmission request, the disk recorder 210transmits the function information to the television receiver 250.

For example, when the television receiver 250 executes switching of HDMIinput at the time of power-on, or the like, the television receiver 250transmits this transmission request to the disk recorder 210 via the CECline 84. In this case, the HDMI reception unit 253 of the televisionreceiver 250 makes up a function information requesting unit, and theHDMI transmission unit 213 of the disk recorder 210 makes up atransmission request reception unit.

Thus, in the case that the television receiver 250 transmits atransmission request to the disk recorder 210, the television receiver250 can confirm at arbitrary timing (e.g., at the time of power-on, atthe time of input switching, or the like) whether or not the diskrecorder 210 is an eHDMI-compatible device, and further the transmissionformat (application) that the disk recorder 210 can support can beconfirmed.

The above description has shown an example wherein the functioninformation is transmitted from the disk recorder 210 to the televisionreceiver 250. Conversely, it can be conceived that the functioninformation is transmitted from the television receiver 250 to the diskrecorder 210, in the same way as described above. In this case, thefunction information cannot be transmitted by inserting this during theblanking period of a video signal, but the function information cantransmit via the CEC line 84 which is the control data line. In thiscase, the HDMI transmission unit 212 of the disc recorder 210 makes up afunction information reception unit, and the HDMI reception unit 252 ofthe television receiver 250 makes up a function information transmissionunit.

Now, transmission/reception of the function information using the CECline (CEC channel) will be described. With this CEC line, transmissionof control data can be executed bidirectionally between a source deviceand a sink device. With the present invention, the above functioninformation is transmitted from a source device to a sink device, orfrom a sink device to a source device as the CEC (Consumer ElectronicsControl) data or CDC (Capability Discovery Channel) data.

FIG. 11 illustrates the structure of CEC data to be transmitted with theCEC line. With the CEC line, one block made up of 10-bit data istransmitted for 4.5 milliseconds. A start bit is disposed at the head,subsequently thereto, a header block is disposed, and thereafter, anarbitrary number (n) of data blocks including desired data to betransmitted are disposed. The function information is included in thedata blocks.

FIG. 12 is a diagram illustrating a structure block of the header block.With the header block, the logical address (Logical Address) of a source(Initiator), and the logical address (Logical Address) of a destination(Destination) are disposed. Each logical address is set according to thetype of each device.

FIG. 13 illustrates logical addresses to be set according to the type ofeach device. As shown in FIG. 13, 16 types of address values from “0” to“15” are set for each type of device. With the logical address of asource (Initiator) and the logical address of a destination(Destination) making up the header block in FIG. 12, the correspondingaddress values are disposed with four bits.

Next, the CDC data will be described. The CDC is defined so as to havethe same physical layer as the CEC, but so as to have a logical layerdifferent from the CEC. The structure of the CDC data is not shown inthe drawing, but is of the same data structure as the data structure ofthe CEC shown in FIG. 11, wherein a start bit is disposed at the head,subsequently thereto, a header block is disposed, and thereafter, anarbitrary number (n) of data blocks including desired data to betransmitted are disposed.

Also, the structure of the header block of the CDC data is not shown inthe drawing, but is the same as the header block of the CEC data shownin FIG. 12 structurally. However, “15” is constantly used as the logicaladdress of a source (Initiator), and the logical address of adestination (Destination) making up the header block, regardless of thetype of device. That is to say, with regard to a source (Initiator),unknown (Unregistered) is used, and with regard to a destination(Destination), broadcast (Broadcast) is used.

Thus, with the transmission of the CDC data, “15” is used as the logicaladdresses (Logical Address) of an initiator and a destination to bedisposed in the head block, and accordingly, the logical address of eachdevice does not have to be obtained. The message according to the CDCdata (CDC message) is a broadcast message of which the initiator isunknown for the CEC, and accordingly, from which device to which devicethis message is addressed is not known.

Therefore, with the CDC message, in order to identify a physicalconnection path, the physical addresses (Physical Address) of a source(Initiator) and a destination (Target) are included without fail in amessage to be disposed in the data block. That is to say, at the time oftransmission of the CDC message, logical addresses are not used, andphysical addresses are used.

With the CEC, a message to the effect that <Feature Abort>“it isincompatible” cannot be returned regarding broadcast messages.Therefore, this situation is taken into consideration, and accordingly,let us say that a message is returned without fail as the CDC.

[CDC Message]

Here, as command messages to be disposed in the data block of the CDCdata, an <Exchange Supported Channels Info> message, and an <ActivateSupported Channels> message are defined. The <Exchange SupportedChannels Info> message is a message used at the time of exchanging thefunction information between two devices. Also, the <Activate SupportedChannels> message is a message used at the time of confirming a channel(transmission format) to be activated actually between two devices, andstarting communication. Each message has a data structure such as thefollowing.

TABLE 1 <Exchange Supported Channels Info> [Physical Address] 2 bytes :PA of Initiator [Physical Address] 2 bytes : PA of Target [SupportedChannels] 1 byte   [Audio Return Channel] 1 bit : if initiator supportsthis channel, set this “1”, else “0”.   [Ethernet Channel] 1 bit : ifinitiator supports this channel, set this “1”, else “0”.   [reserved] 6bits (=000000) <Activate Supported Channels> [Physical Address] 2 bytes: PA of Initiator [Physical Address] 2 bytes : PA of Target [SupportedChannels] 1 byte   [Audio Return Channel] 1 bit : if initiator wants toactivate this channel, set this “1”. : if initiator wants to de-activatethis channel, set this “0”.   [Ethernet Channel] 1 bit : if initiatorwants to activate this channel, set this “1”. : if initiator wants tode-activate this channel, set this “0”.   [reserved] 6 bits (=000000)

The <Exchange Supported Channels Info> message will be described. This<Exchange Supported Channels Info> message has data of five bytes of afirst byte through a fifth byte. The physical address (Physical Address)of a source (Initiator) is disposed in the first and second byte, andthe physical address (Physical Address) of a destination (Target) isdisposed in the third and fourth bytes.

Also, the function information of the source (Initiator) is disposed inthe fifth byte. This function information is information indicating thatit itself is an eHDMI-compatible device, and includes a channel that ititself can support, i.e., the information of a transmission format(application) that the it can support itself.

One bit of the fifth byte, e.g., the seventh bit (most significant bit)indicates that it itself is an eHDMI-compatible device, and whether ornot supporting the transmission format (application) of the above SPDIFsignal, i.e., whether or not supporting the [Audio Return Channel]. Onebit of the fifth byte is set to “1” when supporting this, and is set to“0” when not supporting this.

Also, another one bit of the fifth byte, e.g., the sixth bit indicatesthat it itself is an eHDMI-compatible device, and whether or notsupporting the transmission format (application) of the Ethernet signal,i.e., whether or not supporting the [Ethernet Channel]. Another one bitof the fifth byte is set to “1” when supporting this, and is set to “0”when not supporting this.

Also, the remaining six bits of the fifth byte, e.g., the fifth bitthrough the zero'th bit are set to reserved bits, and are all set to“0”.

Next, the <Activate Supported Channels> message will be described. This<Activate Supported Channels> message includes data of five bytes of thefirst byte through the fifth byte. The physical address (PhysicalAddress) of a source (Initiator) is disposed in the first and secondbyte, and the physical address (Physical Address) of a destination(Target) is disposed in the third and fourth bytes.

Also, the information of a channel (transmission format) that the source(Initiator) asks for activation is disposed in the fifth byte. One bitof the fifth byte, e.g., the seventh bit indicates whether or not ititself asks for communication of the SPDIF signal, i.e., activation ofthe channel of the [Audio Return Channel]. One bit of this fifth byte isset to “1” when asking for activation, and is set to “0” when not askingfor activation.

Also, another one bit of the fifth byte, e.g., the sixth bit indicateswhether or not it itself asks for communication of the Ethernet signal,i.e., activation of the channel of the [Ethernet Channel]. Another onebit of the fifth byte is set to “1” when asking for activation, and isset to “0” when not asking for activation.

Also, the remaining six bits of the fifth byte, e.g., the fifth bitthrough the zero'th bit are set to reserved bits, and are all set to“0”.

The rule of the above <Exchange Supported Channels Info> message and<Activate Supported Channels> message are defined such as the following.That is to say, when a certain CDC device broadcasts the <ExchangeSupported Channels Info> message, the CDC device having the physicaladdress of a destination included in the message thereof broadcasts the<Exchange Supported Channels Info> message including the information(parameters) of itself.

Also, when a certain CDC device broadcasts the <Activate SupportedChannels> message, the CDC device having the physical address (PhysicalAddress) of a destination included in the message thereof broadcasts the<Activate Supported Channels> message including the information(parameters) of itself. Further, with the function information exchangedwith the <Exchange Supported Channels Info> message, of the channels ofthe [Audio Return Channel] and the [Ethernet Channel], when there is achannel (transmission format) supported by both, communication by thechannel thereof can be executed between two devices.

Note that the CDC device means an eHDMI-compatible device that cansupport CDC data <Exchange Supported Channels Info> message, <ActivateSupported Channels> message, and the like. On the other hand, theNon-CDC device means an eHDMI-compatible device that cannot support CDCdata <Exchange Supported Channels Info> message, <Activate SupportedChannels> message, and the like.

[Exchange Sequence]

Next, an example of use of the <Exchange Supported Channels Info>message will be described with reference to the sequence diagram in FIG.14. Note that this case assumes an AV system 10 of the deviceconfiguration shown in FIG. 15. That is to say, the AV system 10 isconfigured of CDC devices 11 and 12, and a Non-CDC device 13. The HDMIterminal 11 a of the CDC device 11, and the HDMI terminal 12 a of theCDC device 12 are connected via an HDMI cable 14. Also, the HDMIterminal 11 b of the CDC device 11, and the HDMI terminal 13 a of theNon-CDC device 13 are connected via an HDMI cable 15. Also, the physicaladdress (Physical Address) of the CDC device 11 is [0.0.0.0], thephysical address (Physical Address) of the CDC device 12 is [1.0.0.0],and the physical address (Physical Address) of the Non-CDC device 13 is[2.0.0.0].

Returning to FIG. 14, (a) the CDC device 11 broadcasts the <ExchangeSupported Channels Info> message to exchange the function informationwith the CDC device 12. The physical address of the source (Initiator)is set to [0.0.0.0], and the physical address of the destination(Target) is set to [1.0.0.0], which are included in the <ExchangeSupported Channels Info> message. Also, the CDC device 11 includes thefunction information of itself in the <Exchange Supported Channels Info>message. For example, this <Exchange Supported Channels Info> messageindicates that both channels of the [Audio Return Channel] and the[Ethernet Channel] are supported.

(b) The CDC device 12 broadcasts the <Exchange Supported Channels Info>message since the physical address of a destination included in the<Exchange Supported Channels Info> message broadcasted from the CDCdevice 11 is the physical address [1.0.0.0] of itself. The physicaladdress of the source (Initiator) is set to [1.0.0.0], and the physicaladdress of the destination (Target) is set to [0.0.0.0], which areincluded in the <Exchange Supported Channels Info> message. Also, theCDC device 12 includes the function information of itself in the<Exchange Supported Channels Info> message. For example, this <ExchangeSupported Channels Info> message indicates that both channels of the[Audio Return Channel] and the [Ethernet Channel] are supported.

Thus, the <Exchange Supported Channels Info> message istransmitted/received between the CDC device 11 and the CDC device 12,whereby the mutual function information, i.e., information indicatingwhether or not an eHDMI-compatible device, and whether or not the [AudioReturn Channel] or [Ethernet Channel] is supported, is exchanged.

(C) The CDC device 11 broadcasts the <Exchange Supported Channels Info>message to exchange the function information with the Non-CDC device 13.The physical address of the source (Initiator) is set to [0.0.0.0], andthe physical address of the destination (Target) is set to [2.0.0.0],which are included in the <Exchange Supported Channels Info> message.Also, the CDC device 11 includes the function information of itself inthe <Exchange Supported Channels Info> message. For example, this<Exchange Supported Channels Info> message indicates that both channelsof the [Audio Return Channel] and the [Ethernet Channel] are supported.

(d) The Non-CDC device 13 does not react at all even if the physicaladdress of a destination included in the <Exchange Supported ChannelsInfo> message broadcasted from the CDC device 11 is the physical address[2.0.0.0] of itself. In this case, with a 2-second limiting rule, whenthere has been no reaction even if two seconds elapses, the CDC device11 recognizes that the Non-CDC device 13 does not support both channelsof the [Audio Return Channel] and the [Ethernet Channel].

[Active/Inactive Sequence]

Next, an example of use of the <Active Supported Channels> message willbe described with reference to the sequence diagram in FIG. 16. Notethat this case assumes a case where, with the AV system 10 having thedevice configuration shown in FIG. 15, as described above, communicationis executed between the CDC device 11 and the CDC device 12 which haveexchanged the function information using the <Exchange SupportedChannels Info> message.

(a) The CDC device 11 broadcasts the <Active Supported Channels> messageto confirm the channel (transmission format) to be asked for activationactually so as to start communication with the CDC device 12. Thephysical address of the source (Initiator) is set to [0.0.0.0], and thephysical address of the destination (Target) is set to [1.0.0.0], whichare included in this <Active Supported Channels> message. Also, the CDCdevice disposes the information of the channel (transmission format)which it itself asks for activation, in this <Active Supported Channels>message. For example, this <Active Supported Channels> message indicatesthat activation for both channels of the [Audio Return Channel] and the[Ethernet Channel] is requested.

(b) The CDC device 12 broadcasts the <Active Supported Channels> messagesince the physical address of the destination included in the <ActiveSupported Channels> message broadcasted from the CDC device 11 is thephysical address [1.0.0.0] of itself. The physical address of the source(Initiator) is set to [1.0.0.0], and the physical address of thedestination (Target) is set to [0.0.0.0], which are included in this<Active Supported Channels> message. Also, the CDC device 12 disposesthe information of the channel (transmission format) wherein it itselfagrees with the request for activation, in this <Active SupportedChannels> message. For example, this <Active Supported Channels> messageindicates that the request for activation of both channels of the [AudioReturn Channel] and the [Ethernet Channel] is approved.

Thus, the <Active Supported Channels> message is transmitted/receivedbetween the CDC device 11 and the CDC device 12, whereby both of the CDCdevice 11 and the CDC device 12 confirm the channel (transmissionformat) which can be shared and activated, and communication is started.With the example in FIG. 16, both of the CDC device 11 and the CDCdevice 12 can activate the [Audio Return Channel] and the [EthernetChannel], and accordingly, both channels (transmission formats) areactivated, and communication is started.

(c) Subsequently, for example, in the case of intending to stop thecommunication of the [Ethernet Channel] to execute Ethernetcommunication via a network terminal, the CDC device 12 broadcasts the<Active Supported Channels> message. The physical address of the source(Initiator) is set to [1.0.0.0], and the physical address of thedestination (Target) is set to [0.0.0.0], which are included in this<Active Supported Channels> message. Also, this <Active SupportedChannels> message indicates that the channel (transmission format) whichthe CDC device 12 itself asks for activation is the channel of the[Audio Return Channel], and the channel of the [Ethernet Channel] isremoved.

(d) The CDC device 11 broadcasts the <Active Supported Channels> messagesince the physical address of the destination included in the <ActiveSupported Channels> message broadcasted from the CDC device 12 is thephysical address [0.0.0.0] of itself. The physical address of the source(Initiator) is set to [0.0.0.0], and the physical address of thedestination (Target) is set to [1.0.0.0], which are included in this<Active Supported Channels> message. Also, the CDC device 11 disposesthe information of the channel (transmission format) wherein it itselfagrees with the request for activation in this <Active SupportedChannels> message. For example, this <Active Supported Channels> messageindicates that the request for activation of the channel of the [AudioReturn Channel] is approved.

Thus, the <Active Supported Channels> message is transmitted/receivedbetween the CDC device 11 and the CDC device 12, whereby both of the CDCdevice 11 and the CDC device 12 reconfirm the channel (transmissionformat) which can be shared and activated, communication with thechannel of the [Ethernet Channel] is stopped, and only communicationwith the channel of the [Audio Return Channel] is continued.

Next, another example of use of the <Active Supported Channels> messagewill be described with reference to the sequence diagram in FIG. 17.Note that this case assumes a case where, with the AV system 10 havingthe device configuration shown in FIG. 15, as described above,communication is executed between the CDC device 11 and the CDC device12 which have exchanged the function information using the <ExchangeSupported Channels Info> message.

(a) The CDC device 11 broadcasts the <Active Supported Channels> messageto confirm the channel (transmission format) to be asked for activationactually so as to start communication with the CDC device 12. Thephysical address of the source (Initiator) is set to [0.0.0.0], and thephysical address of the destination (Target) is set to [1.0.0.0], whichare included in this <Active Supported Channels> message. Also, the CDCdevice 11 disposes the information of the channel (transmission format)which it itself asks for activation, in this <Active Supported Channels>message. For example, this <Active Supported Channels> message indicatesthat activation for both channels of the [Audio Return Channel] and the[Ethernet Channel] is requested.

(b) The CDC device 12 broadcasts the <Active Supported Channels> messagesince the physical address of the destination included in the <ActiveSupported Channels> message broadcasted from the CDC device 11 is thephysical address [1.0.0.0] of itself. The physical address of the source(Initiator) is set to [1.0.0.0], and the physical address of thedestination (Target) is set to [0.0.0.0], which are included in this<Active Supported Channels> message. Also, the CDC device 12 disposesthe information of the channel (transmission format) wherein it itselfagrees with the request for activation, in this <Active SupportedChannels> message. For example, this <Active Supported Channels> messageindicates that the request for activation of the channel of the [AudioReturn Channel] is approved.

Thus, the <Active Supported Channels> message is transmitted/receivedbetween the CDC device 11 and the CDC device 12, whereby both of the CDCdevice 11 and the CDC device 12 confirm the channel (transmissionformat) which can be shared and activated, and communication is started.With the example in FIG. 16, the CDC device 11 asks for activation ofboth channels of the [Audio Return Channel] and the [Ethernet Channel],but the CDC device 12 agrees with activation of only the channel of the[Audio Return Channel], and accordingly, only the channel of the [AudioReturn Channel] is activated, and communication is started.

Note that transmission/reception of the above <Active SupportedChannels> message is executed, for example, after exchange of thefunction information is executed using the <Exchange Supported ChannelsInfo> message, and both of the functions are known each other.Thereafter, transmission/reception of the <Active Supported Channels>message is executed at arbitrary timing, such as at the time of changeof the desired channel for communication, or the like.

[Improvement of Validity of CDC Message]

As described above, the physical addresses (Physical Address) of thesource (Initiator) and the destination (Target) are arranged to beincluded in the CDC message without fail. For example, in the case thata sink device includes multiple HDMI terminals, with a source deviceconnected to a predetermined port (HDMI terminal) where the HPD signalis “L”, the physical address (Physical Address) thereof is unfixed.Thus, when the physical address is unfixed, the validity of the aboveCDC message decreases. Therefore, in such a case, an example whereinimprovement of the validity of the CDC message is realized will bedescribed below.

Example 1

With this example 1, a direct mode (Direct Mode) bit is provided to the<Active Supported Channels> message and the <Exchange Supported ChannelsInfo> message, thereby realizing improvement of the validity of the CDCmessage. In this case, the <Exchange Supported Channels Info> messageand the <Active Supported Channels> message have a data structure, forexample, such as shown in the following.

TABLE 2 <Exchange Supported Channels Info> [Physical Address] 2 bytes :PA of Initiator [Physical Address] 2 bytes : PA of Target [SupportedCapabilities] 1 byte   [Direct Mode] 1 bit : if initiator supportscommunication in HPD=L set this “1”, else “0”.   [Audio Return Channel]1 bit : if initiator supports Audio Return Channel, set this “1”, else“0”.   [Ethernet Channel] 1 bit : if initiator supports EthernetCommunication, set this “1”, else “0”.   [reserved] 5 bits (=00000)<Activate Supported Channels> [Physical Address] 2 bytes : PA ofInitiator [Physical Address] 2 bytes : PA of Target [SupportedCapabilities] 1 byte   [Direct Mode] 1 bit : indicate Direct Mode (1) ornot (0)   [Audio Return Channel] 1 bit : if initiator wants to activateAudio Return Channel, set this “1”. : if initiator wants to de-activateAudio Return Channel, set this “0”.   [Ethernet Channel] 1 bit : ifinitiator wants to activate Ethernet Communication, set this “1”. ifinitiator wants to de-activate Ethernet Communication set this “0”.  [reserved] 5 bits (=00000)

The <Exchange Supported Channels Info> message will be described. This<Exchange Supported Channels Info> message includes data of five bytesof the first byte through the fifth byte. The physical address (PhysicalAddress) of a source (Initiator) is disposed in the first and secondbytes, and the physical address (Physical Address) of a destination(Target) is disposed in the third and fourth bytes.

Also, the function information of the source (Initiator) is disposed inthe fifth byte. This function information has information indicatingthat it itself supports the direct mode. Also, this function informationhas information indicating that it itself is an eHDMI-compatible device,and includes the information of the channel that it can support itself.That is to say, one bit of the fifth byte, for example, the seventh bitindicates whether or not supporting the direct mode. One bit of thisfifth byte is set to “1” when supporting the direct mode, and is set to“0” when not supporting the direct mode.

Also, another one bit of the fifth byte, for example, the sixth bitindicates that it itself is an eHDMI-compatible device, and supports theabove SPDIF signal, i.e., whether or not supporting the [Audio ReturnChannel]. Another bit of the fifth byte is set to “1” when supportingthe [Audio Return Channel], and is set to “0” when not supporting the[Audio Return Channel].

Also, another one bit of the fifth byte, for example, the fifth bitindicates that it itself is an eHDMI-compatible device, and whether ornot supporting the above Ethernet signal, i.e., whether or notsupporting the [Ethernet Channel]. Another bit of the fifth byte is setto “1” when supporting the [Ethernet Channel], and is set to “0” whennot supporting the [Ethernet Channel]. Also, the remaining five bits ofthe fifth byte, e.g., the fourth bit through the zero'th bit are set toreserved bits, and are all set to “0”.

Next, the <Active Supported Channels> message will be described. This<Active Supported Channels> message includes data of five bytes of thefirst byte through the fifth byte. The physical address (PhysicalAddress) of a source (Initiator) is disposed in the first and secondbytes, and the physical address (Physical Address) of a destination(Target) is disposed in the third and fourth bytes. Also, informationindicating whether or not this message is a message according to thedirect mode, and the information of a channel (transmission format)which the source (Initiator) asks for activation, is disposed in thefifth byte.

That is to say, one bit of the fifth byte, e.g., the seventh bitindicates whether or not this message is a message according to thedirect mode. This one bit of the fifth byte is set to “1” at the time ofa message according to the direct mode, and is set to “0” at the time ofnot a message according to the direct mode but a common message. Anotherone bit of the fifth byte, e.g., the sixth bit indicates whether or notit itself asks for communication of the SPDIF signal, i.e., activationof the channel of the [Audio Return Channel]. This other one bit of thefifth byte is set to “1” when asking for activation, and is set to “0”when not asking for activation.

Also, another one bit of the fifth byte, e.g., the fifth bit indicateswhether or not it itself asks for communication of the Ethernet signal,i.e., activation of the channel of the [Ethernet Channel]. This otherone bit of the fifth byte is set to “1” when asking for activation, andis set to “0” when not asking for activation. Also, the remaining fivebits of the fifth byte, e.g., the fourth bit through the zero'th bit areset to reserved bits, and are all set to “0”.

As described above, in the case that a direct mode bit is provided toeach message, for example, the following operation is executed. That isto say, at the time of exchange of the function information according tothe <Active Supported Channels> message, confirmation is made whether ornot supporting communication with the HPD signal as “L”, i.e., thedirect mode. Subsequently, in the case that support for the direct modehas been confirmed, transmission/reception of the <Exchange SupportedChannels Info> message is executed in the direct mode.

The source (Initiator) is allowed to transmit the CDC message in thedirect mode between two CDC devices which support the direct mode. Thesource (Initiator) does not transmit the same CDC message to other CDCdevices, and also the destination (Target) does not transfer thereceived CDC message to other CDC devices.

For example, let us consider a configuration example of an AV system 20such as shown in FIG. 18. A CDC device 21 which is a source (Initiator)includes three ports 21 a through 21 c. A CDC device 22 which is adestination (Target) includes four ports 22 a through 22 d. The port 21a of the CDC device 21, and the port 22 a of the CDC device 22 which isthe destination (Target) are connected.

In this case, in the event that the CDC device 21 which is the source(Initiator) transmits the CDC message to the CDC device 22 which is thedestination (Target), this CDC device 22 outputs the CDC message to theport 21 a, but does not output the same CDC message to the other ports21 b and 21 c. Also, the CDC device 21 which is the source (Initiator)does not transfer the CDC message transmitted to the port 22 a in thedirect mode to the other ports 22 b through 22 d.

As described above, the CDC device which supports the direct mode has afunction for subjecting the CDC message to filtering. However, themethod of filtering is an issue of processing within a device, andaccordingly, there is no need to be defined as a transmission standard.

As described above, the direction mode is provided, wherebytransmission/reception of the CDC message can be executed between twoCDC devices alone, and accordingly, even if the HPD signal is “L”, andthe physical address (Physical Address) of a source device side isunfixed, the validity of the CDC message is not deteriorated.

Example 2

With this Example 2, in addition to the <Active Supported Channels>message and the <Exchange Supported Channels Info> message, a <RequestHPD=H> message for requesting that the HPD signal is set to “H” isadded, a source device is allowed to read the physical address (PhysicalAddress) of itself from a sink device, thereby realizing improvement ofthe validity of the CDC message. The <Request HPD=H> message has a datastructure, for example, such as shown in the following.

[Table 3]

<Request HPD=H>: no operands

A CDC device (source device) wherein the HPD signal is “L”, and thephysical address (Physical Address) of itself is unfixed, broadcasts theabove <Request HPD=H> message. The CDC device which has received the<Request HPD=H> message sequentially sets the HPD signal at each port to“H” at least for a predetermined period of time, e.g., just for fiveminutes. The CDC device which has broadcasted the <Request HPD=H>message reads out the E-EDID to obtain the physical address of itselfduring a period while the HPD signal of the port of the CDC device (sinkdevice) connected to itself is “H”.

Thus, the CDC device (source device) wherein the HPD signal is “L”, andthe physical address of itself is unfixed uses the <Request HPD=H>message, whereby the physical address of itself can be obtained anddetermined, and accordingly, the validity of the CDC message can beimproved.

Example 3

With this Example 3 as well, in addition to the <Active SupportedChannels> message and the <Exchange Supported Channels Info> message, a<Request HPD=H> message for requesting that the HPD signal is set to “H”is added, a source device is allowed to read the physical address(Physical Address) of itself from a sink device, thereby realizingimprovement of the validity of the CDC message.

In the case of the above Example 2, each CDC device which has receivedthe <Request HPD=H> message sequentially sets the HPD signal at eachport to “H”. Therefore, the CDC device which has output the <RequestHPD=H> message has to wait for the HPD signal of the port of the CDCdevice (sink device) connected to itself to become “H”. In this case, ifthe hierarchy of the CDC device connected to itself is known, and onlythe CDC devices of this hierarchy set the HPD signal of each port to“H”, obtaining of the physical address can be executed rapidly.

Therefore, data for specifying the hierarchy of the physical address tobe asked for setting the HPD signal to “H” is added to the <RequestHPD=H> message of this Example 3. Also, with this Example 3, a <ReportHPD=H> message is added. This <Report HPD=H> message is a CDC messagethat the CDC device which has set the HPD signal to “H” broadcasts, andincludes the physical address of this CDC device. The <Request HPD=H>message and the <Report HPD=H> message have a data structure, forexample, such as the following.

TABLE 4 <Request HPD=H> [Requested Layer] 4 bits : This fields indicatePA layer of the CDC device.   [A of PA (A.B.C.D)] 1 bit : request tox.0.0.0   [B of PA (A.B.C.D)] 1 bit : request to z.x.0.0   [C of PA(A.B.C.D)] 1 bit : request to z.z.x.0   [D of PA (A.B.C.D)] 1 bit :request to z.z.z.x <Report HPD=H> [Physical Address] 2 bytes : PA ofHPD=H

The <Request HPD=H> message will be described. This <Request HPD=H>message includes data of four bits of the third bit through the zero'thbit for specifying the hierarchy of the physical address. The third bitis set to “1”, and the other bits are set to “0”, thereby specifying thefirst hierarchy (most significant hierarchy) of the physical address.Also, the second bit is set to “1”, and the other bits are set to “0”,thereby specifying the second hierarchy, or the first and secondhierarchies of the physical address. Also, the first bit is set to “1”,and the other bits are set to “0”, thereby specifying the thirdhierarchy, or the first through third hierarchies of the physicaladdress. Also, the zero'th bit is set to “1”, and the other bits are setto “0”, thereby specifying the fourth hierarchy, or the first throughfourth hierarchies of the physical address.

Also, the <Report HPD=H> message will be described. This <Report HPD=H>message includes data of two bytes. The physical address of the CDCdevice of which the HPD signal has been set to “H”, i.e., the physicaladdress (Physical Address) of the source (Initiator) is disposed in thetwo bytes thereof.

Example 4

This Example 4 is an example wherein instead of using the <RequestHPD=H> message such as the above Example 2 and Example 3, the voltage ofthe power supply line is changed, thereby requesting for setting the HPDsignal to “H”. Specifically, the CDC device (source device) connected toa predetermined port of the CDC device (sink device) of which the HPDsignal is “L” temporarily resets the voltage of the power supply line toground voltage such as shown in FIG. 19( b), and then raises the powersupply line to +5V.

In response to voltage change in this power supply line, the CDC device(sink device) sets the HPD signal at the predetermined port to “H” atleast for a predetermined period of time, e.g., just for five minutes,such as shown in FIG. 19( a). Thus, the CDC device (source device) readsout the E-EDID from the CDC device (sink device) while the predeterminedport of the HPD signal is “H” to obtain the physical address of itself.

Thus, the CDC device (source device) wherein the HDP signal is “L”, andthe physical address of itself is unfixed changes the voltage of thepower supply line, whereby the physical address of itself can beobtained from the CDC device (sink device) and determined, andaccordingly, the validity of the CDC message can be improved.

Note that, with the above description, an arrangement has been madewherein, for example, from the disk recorder 210 to the televisionreceiver 250, the function information is inserted and transmittedduring the blanking period of a video signal, or the functioninformation is transmitted via the CEC line 84 which is the control dataline, whereby the television receiver 250 side can be allowed torecognize whether or not this disk recorder 210 is an eHDMI-compatibledevice.

However, an arrangement may be made wherein the voltage of the firstline, e.g., the reserve line of the HDMI cable 350 is changed, wherebythe function information, and further, compatible transmission formatinformation can be transmitted.

First Example

The disk recorder 210 changes the voltage of the first line, e.g., thereserve line of the HDMI cable 350, thereby notifying the televisionreceiver 250 that it itself is an eHDMI-compatible device.

The television receiver 250 detects the voltage change in the reserveline, thereby obtaining the function information indicating that thedisk recorder 210 is an eHDMI-compatible device. In this case, the CPU271 of the television receiver 250 makes up a function informationobtaining unit.

Also, the disk recorder 210 may automatically change the voltage of thereserve line at the time of the television receiver 250 being connectedthereto via the HDMI cable 350, or may change the voltage of the reserveline at timing requested from the television receiver 250 side. The diskrecorder 210 determines whether or not there has been a request from thetelevision receiver 250 side according to the voltage change of thesecond line, e.g., the HPD line of the HDMI cable 350. In this case, theCPU 271 of the television receiver 250 makes up a function informationrequesting unit, and the CPU 221 of the disk recorder 210 makes up avoltage change detecting unit.

Also, the disk recorder 210 can also notify the television receiver 250of the information of the transmission format (application) that itsupports itself by changing the voltage of the reserve line in a pulseshape in addition to that it itself is an eHDMI-compatible device. Here,the transmission format information is information indicating whether ornot supporting only the SPDIF signal, whether or not supporting only theEthernet signal, whether or not supporting both of the SPDIF signal andthe Ethernet signal, or the like. In this case, the CPU 271 of thetelevision receiver 250 makes up a format information obtaining unit.

For example, let us define that a pulse count 1 is compatible with onlythe SPDIF signal, a pulse count 2 is compatible with only the Ethernetsignal, and a pulse count is compatible with both of the SPDIF signaland the Ethernet signal.

Also, for example, let us define that the pulse count 1 is compatiblewith eHDMI (unknown transmission format), the pulse count 2 iscompatible with only the SPDIF signal, the pulse count 3 is compatiblewith only the Ethernet signal, and the pulse count 4 is compatible withboth of the SPDIF signal and the Ethernet signal.

Also, for example, let us define that the pulse count 1 is compatiblewith eHDMI (unknown transmission format), the pulse count 2 iscompatible with only the SPDIF signal, the pulse count 3 is compatiblewith only the Ethernet signal, the pulse count 4 is compatible with bothof the SPDIF signal and the Ethernet signal, and the pulse count 5 isreserve.

Thus, in the case that, with the disk recorder 210 side, the voltage ofthe reserve line is changed in a pulse shape according to the compatibletransmission format, the television receiver 250 side can obtain theinformation of the transmission format that the disk recorder 210supports based on the pulse count. Note that it can be conceived thatthe compatible transmission format (application) is represented with thevoltage level or pulse phase instead of the pulse count.

FIG. 20 illustrates a configuration example of the disk recorder 210 andthe television receiver 250 in the case of changing the voltages of thereserve line and the HPD line, as described above. In FIG. 20, theportions corresponding to those in FIG. 8 are denoted with the samereference numerals, and detailed description will be omitted.

With the disk recorder 210, the pin 14 of the HDMI terminal 211 isgrounded via a connection switch 418 made up of a transistor and thelike. On/off of this connection switch 418 is controlled with a controlsignal SW1 from the CPU 221 (see FIG. 2). Thus, the television receiver250 can be notified that the disk recorder 210 is an eHDMI-compatibledevice by changing the voltage of the reserve line, and also the changethereof is represented with a pulse shape, whereby the televisionreceiver 250 can also be notified of compatible transmission format(application) information. In this case, the connection switch 418 andthe CPU 221 make up a function information transmission unit and aformat information transmission unit.

Also, with the television receiver 250, the pin 19 of the HDMI terminal251 is grounded via a connection switch 450 made up of a transistor andthe like. On/off of this connection switch 450 is controlled with acontrol signal SW2 from the CPU 271 (see FIG. 3). Thus, the televisionreceiver 250 can request the disk recorder 210 to notify informationregarding whether or not this disk recorder 210 is an eHDMI-compatibledevice by changing the voltage of the HPD line. In this case, theconnection switch 450 and the CPU 271 make up a function informationrequesting unit. With this television receiver 250, the functioninformation indicating that the disk recorder 210 is an eHDMI-compatibledevice, and further, compatible transmission format information, can beobtained from the voltage Vrsv of the pin 14 of the HDMI terminal 251.

FIG. 21 illustrates a voltage control example of the HPD line on thetelevision receiver (sink device) 250 side, and a voltage controlexample of the reserve line on the disk recorder (source device) 210side corresponding thereto. In the case of this example, first, as shownin FIG. 21( a), the connection switch 450 of the television receiver 250is set to an on state from an off state just for a predetermined periodof time, and the voltage of the HPD (eHDMMI−) line is changed from lowto high. Thus, a request is executed from the television receiver 250 tothe disk recorder 210 so as to notify the function information and thelike.

On the other hand, after the voltage of the HPD line is restored to ahigh state, the connection switch 418 of the disk recorder 210 is setfrom an off state to an on state, the voltage of the reserve line ischanged from high to low as shown in FIG. 21( b), and the functioninformation indicating that the disk recorder 210 is an eHDMI-compatibledevice is transmitted from the disk recorder 210 to the televisionreceiver 250.

Thereafter, for example, during 100 msec., the connection switch 418 ofthe disk recorder 210 is subjected to switching control, and the voltageof the reserve line is changed from low to high repeatedly according tothe transmission format that the disk recorder 210 can support. Thus,the transmission format information that the disk recorder 210 cansupport is transmitted from the disk recorder 210 to the televisionreceiver 250. Finally, the connection switch 418 is returned to an offstate.

As shown in FIG. 21( b), the voltage of the reserve line has beenchanged, and accordingly, with the television receiver 250, the voltageof the reserve line is detected, whereby function information can beobtained wherein, for example, the disk recorder 210 is aneHDMI-compatible device, and further, the pulse count is three, andaccordingly, for example, the disk recorder 210 supports both of theSPDIF signal and the Ethernet signal.

As described above, after the function information indicating that thedisk recorder 210 is an eHDMI-compatible device, the compatibletransmission format information transmitted from the disk recorder 210is confirmed at the television receiver 250, and eHDMI transmission isstarted between the television receiver 250 and disk recorder 210.

Second Example

With the above first example, the voltage of the first line, e.g., thereserve line of the HDMI cable 350 is changed, thereby transmittingfunction information indicating that the disk recorder 210 is aneHDMI-compatible device, and compatible transmission format informationfrom the disk recorder 210 to the television receiver 250.

With this second example, the voltage of the reserve line of the HDMIcable 350 is further changed, the information of a transmission formatthat the television receiver 250 can support is transmitted from thetelevision receiver 250 to the disk recorder 210. With this secondexample, detailed description regarding the portions corresponding tothose in the first example will be omitted.

After obtaining function information indicating that the disk recorder210 is an eHDMI-compatible device, and compatible transmission formatinformation by detecting voltage change in the reserve line, thetelevision receiver 250 changes the voltage of the reserve line in apulse shape to notify the disk recorder 210 of the information of atransmission format that it itself supports. In this case, the CPU 271of the television receiver 250 makes up a format informationtransmission unit. The disk recorder 210 detects voltage change in thereserve line, thereby obtaining the information of the transmissionformat that the television receiver 250 supports. In this case, the CPU221 of the disk recorder 210 makes up a format information obtainingunit.

FIG. 22 illustrates a configuration example of the disk recorder 210 andthe television receiver 250, as described above, in the case that thefunction information and the compatible transmission format informationis transmitted from the disk recorder 210 to the television receiver250, and also the compatible transmission format information istransmitted from the television receiver 250 to the disk recorder 210.In FIG. 22, the portions corresponding to those in FIG. 20 are denotedwith the same reference numerals, and detailed description thereof willbe omitted.

With the television receiver 250, the pin 14 of the HDMI terminal 251 isgrounded via a connection switch 451 made up of a transistor and thelike. On/off of this connection switch 451 is controlled with a controlsignal SW3 from the CPU 271. Thus, the television receiver 250 cannotify the disk recorder 210 of the information of a transmission formatthat it itself supports by changing the voltage of the reserve line in apulse shape. In this case, the connection switch 451 and the CPU 271make up a format information transmission unit. The other configurationsof the television receiver 250 in FIG. 22 are the same as those in thetelevision receiver 250 in FIG. 20.

Note that the configuration of the disk recorder 210 in FIG. 22 is thesame as the configuration of the disk recorder 210 in FIG. 20. With thisdisk recorder 210, the information of a transmission format that thetelevision receiver 250 supports can be obtained from the voltage Vrsvof the pin 14 of the HDMI terminal 211, as described above. In thiscase, the CPU 221 of the disk recorder 210 makes up a format informationobtaining unit.

FIG. 23 illustrates a voltage control example of the HPD line on thetelevision receiver (sink device) 250 side, and a voltage controlexample of the reserve line on the disk recorder (source device) 210side and the television receiver (sink device) 250 side correspondingthereto.

In the case of this example, first, as shown in FIG. 23( a), theconnection switch 450 of the television receiver 250 is set to an onstate from an off state just for a predetermined period of time, and thevoltage of the HPD (eHDMMI−) line is changed from low to high. Thus, arequest is executed from the television receiver 250 to the diskrecorder 210 so as to notify the function information and the like.

On the other hand, after the voltage of the HPD line is restored to ahigh state, the connection switch 418 of the disk recorder 210 is setfrom an off state to an on state, the voltage of the reserve line ischanged from high to low as shown in FIG. 23( b), and the functioninformation indicating that the disk recorder 210 is an eHDMI-compatibledevice is transmitted from the disk recorder 210 to the televisionreceiver 250.

Thereafter, for example, during 100 msec., the connection switch 418 ofthe disk recorder 210 is subjected to switching control, and the voltageof the reserve line is changed from low to high repeatedly according tothe transmission format that the disk recorder 210 can support. Thus,the information of a transmission format that the disk recorder 210 cansupport is transmitted from the disk recorder 210 to the televisionreceiver 250 (declaration of transmittable format for the source side).Finally, the connection switch 418 is returned to an off state.

Also, thereafter, during 100 msec. for example, the connection switch451 of the television receiver 250 is subjected to switching control,and as shown in FIG. 23( b), the voltage of the reserve line is changedfrom low to high repeatedly according to the transmission format thatthe television receiver 250 can support. Thus, the information of atransmission format that the television receiver 250 can support istransmitted from the television receiver 250 to the disk recorder 210(declaration of a transmittable format on the sink side). Finally, theconnection switch 451 is returned to an off state.

As described above, with the television receiver 250, the functioninformation indicating that the disk recorder 210 is an eHDMI-compatibledevice, and the compatible transmission format information transmittedfrom the disk recorder 210 is confirmed, and with the disk recorder 210,the compatible transmission format information transmitted from thetelevision receiver 250 is confirmed, and then eHDMI transmission isstarted between the television receiver 250 and the disk recorder 210.

Now, description will be made regarding a case where the televisionreceiver 250 includes multiple HDMI terminals (HDMI ports). Thetelevision receiver 250 shown in the above FIG. 3 includes a single HDMIterminal. FIG. 24 illustrates the television receiver 250 includingmultiple, e.g., three HDMI terminals. In this FIG. 24, the portionscorresponding to those in FIG. 3 are denoted with the same referencenumerals, and detailed description thereof will be omitted.

This television receiver 250 includes HDMI terminals 251 a through 251c, an HDMI switcher 255, and high-speed data line interfaces 253 athrough 253 c. The HDMI switcher 255 selectively connects the HDMIterminals 251 a through 251 c to the HDMI reception unit 252. With theHDMI reception unit 252, the data of video (image) and audio to be inputvia the HDMI cable is obtained at the HDMI terminal connected theretovia the HDMI switcher 255, of the HDMI terminals 251 a through 251 c.

The high-speed data line interfaces 253 a through 253 c arebidirectional communication path interfaces made up of predeterminedlines (the reserve line and HPD line) of the HDMI cable to be connectedto the above HDMI terminals 251 a through 251 c. The high-speed dataline interfaces 253 a through 253 c are inserted between the Ethernetinterface 274 and the HDMI terminals 251 a through 251 c. The high-speeddata line interfaces 253 a through 253 c are configured in the same wayas the high-speed data line interface 253 in FIG. 3.

The other units of the television receiver 250 in FIG. 24 are configuredin the same way as those of the television receiver 250 shown in FIG. 3,and execute the same operation.

As described above, the disk recorder 210 changes the voltage of thereserve line after receiving a transmission request (trigger) for thefunction information and the like from the television receiver 250according to voltage change in the HPD line, and transmits the functioninformation and the like to the television receiver 250.

Therefore, the television receiver 250 can execute a transmissionrequest for the function information and the like in series as to adevice such as the disk recorder 210 or the like connected to each ofthe HDMI terminals via the HDMI cable at arbitrary timing for each HDMIterminal such as shown in FIGS. 25( a) through (c). Thus, reduction inthe number of pins of the microcomputer (CPU 271) is anticipated.

Note that, in FIGS. 25( a) through (c), “DDC5V” denotes the voltage ofthe power supply line, “HPD” denotes the voltage of the HPD line, and“Rsv” denotes the voltage of the reserve line. Input 3 in FIG. 25( c)illustrates that the power supply source of a device has been turned on,or connection has been performed, halfway.

Also, “Source” denotes the function information indicating being aneHDMI-compatible device, and the compatible transmission formatinformation to be transmitted from a source device (e.g., disk recorder210) to a sink device (e.g., television receiver 250). Also, “Sink”denotes the compatible transmission format information to be transmittedfrom a sink device (e.g., television receiver 250) to a source device(e.g., disk recorder 210).

The flowchart in FIG. 26 illustrates an example of a processingprocedure at the time of the CPU 271 of the television receiver (sinkdevice) 250 executing a detection operation as to predetermined HDMIinput.

In step ST1, the CPU 271 starts the processing, and then proceeds toprocessing in step ST2. In this step ST2, the CPU 271 determines whetheror not the voltage (DDC5V) of the power supply line is 5V.

When the voltage (DDC5V) of the power supply line is 5V, in step ST3 theCPU 271 determines whether or not another HDMI input is currentlyperforming a detection operation of the function information, compatibletransmission format information, and the like. At the time of currentlyperforming a detection operation of another input, in step ST4 the CPU271 determines whether or not detection of another input has ended.

At the time of detection of another input having ended, the CPU 271proceeds to processing in step ST5. Note that when another input is notcurrently performing a detection operation, the CPU 271 immediatelyproceeds to the processing in step ST5. In this step ST5, the CPU 271changes the voltage of the HPD line from low to high, and requests asource device on the partner side (disk recorder 210 or the like) oftransmission of the function information and the like.

Next, in step ST6, the CPU 271 monitors the voltage of the reserve lineto determine whether or not reply has been received from the sourcedevice, i.e., whether or not the function information and the like hasbeen transmitted. When no reply has been received, in step ST7 the CPU271 determines whether or not 100 milliseconds have elapsed since atransmission request was performed in step ST5. At the time of 100milliseconds having not elapsed, the CPU 271 returns to the processingin step ST6. On the other hand, at the time of 100 milliseconds havingelapsed, in step ST8 the CPU 271 determines that the source device onthe partner side is an eHDMI-incompatible device.

FIG. 27 illustrates a voltage change example of the HPD line and thereserve line in the case of the CPU 271 determining that the sourcedevice on the partner side is an eHDMI-incompatible device. Note thatFIG. 27( a) illustrates the voltage (DDC5V) of the power supply line,FIG. 27( b) illustrates the voltage of the HPD line, and FIG. 27( c)illustrates the voltage of the reserve line.

As shown in FIG. 27( b), with the television receiver 250, the voltageof the HPD line has been changed from low to high, and a transmissionrequest for the function information and the like has been transmittedto the source device (disk recorder 210 or the like) on the partnerside. However, as shown in FIG. 27( c), thereafter, even if 100milliseconds have elapsed, the voltage of the reserve line is stillhigh, and there have been no reply from the source device.

Returning to the flowchart in FIG. 26, at the time of reply having beenreceived in step ST6, in step ST9 the CPU 271 recognizes that the sourcedevice on the partner side is an eHDMI-compatible device, and alsodetects the compatible transmission format of the source device on thepartner side from voltage change in the reserve line.

Next, in step ST10, the CPU 271 changes the voltage of the reserve linein a pulse shape to transmit the information of a transmission format(application) that the television receiver 250 supports to the sourcedevice on the partner side. Subsequently, in step ST11, the CPU 271starts transmission/reception of an eHDMI signal with the source deviceon the partner side.

With the processing of the flowchart in FIG. 26, at the time of replyfrom the source device having not been received even if 100 millisecondshave elapsed, the CPU 271 immediately determines that the source deviceis an eHDMI-incompatible device. However, as shown in FIG. 28( b), atthe time of reply from the source device having not been received evenif 100 milliseconds have elapsed, the CPU 271 may execute retryprocessing wherein the voltage of the HPD line is changed from low tohigh several times (only once is shown in FIG. 28( b)) to requesttransmission of the function information and the like, as to the partnersource device (disk recorder 210 or the like). Thus, in the case thatthe source device has had difficulty in reply due to a busy state, amistake of immediately determining that the source device is aneHDMI-incompatible device can be avoided.

Note that FIG. 28( a) illustrates the voltage (DDC5V) of the powersupply line, FIG. 28( b) illustrates the voltage of the HPD line, andFIG. 28( c) illustrates the voltage of the reserve line. FIGS. 28( a)and (c) are the same as FIGS. 27( a) and (c).

The flowchart in FIG. 29 illustrates an example of the processingprocedure of the CPU 221 of the disk recorder (source device) 210.

In step ST21, the CPU 221 starts the processing, and then proceeds toprocessing in step ST22. In this step ST22, the CPU 221 determineswhether or not the voltage of the reserve line is in a high state. Whenthe voltage of the reserve line is not high, in step ST23 the CPU 221determines that the sink device on the partner side (television receiver250 or the like) is an eHDMI-incompatible device.

When the voltage of the reserve line is high, the CPU 221 proceeds toprocessing in step ST24. In this step ST24, the CPU 221 determineswhether or not the voltage of the HPD line has been changed from high,low, and high. At the time of such change, the CPU 221 determines that atransmission request for the function information and the like has beenreceived from the sink device on the partner side. Subsequently, in stepST25, the CPU 221 changes the voltage of the reserve line to transmitthe function information indicating that the source device is aneHDMI-compatible device, and the information of a compatibletransmission format (application) to the sink device on the partnerside.

Next, in step ST26, the CPU 221 monitors the voltage of the reserve lineto determine whether or not there has been received reply from the sinkdevice, i.e., whether or not the information of a transmission formatthat the sink device on the partner side can support has beentransmitted. At the time of reply having not been received, in stepST27, the CPU 221 determines whether or not 100 milliseconds haveelapsed since the function information of itself and the like wastransmitted in step ST25. At the time of 100 milliseconds having notelapsed, the CPU 221 returns to the processing in step ST26. On theother hand, at the time of 100 milliseconds having elapsed, in step ST28the CPU 221 determines that the sink device on the partner side is aneHDMI-incompatible device, or incapable of transmission in a busy state.

At the time of reply having been received from the sink side in stepST26, in step ST29 the CPU 221 detects the compatible transmissionformat of the sink device on the partner side from voltage change in thereserve line. Subsequently, in step ST30, the CPU 221 startstransmission/reception of an eHDMI signal with the sink device on thepartner side.

Third Example

With the above first example and second example, the voltage of thesecond line, e.g., the HPD line of the HDMI cable 350 is changed,thereby transmitting a transmission request for the function informationand the like from the television receiver (sink device) 250 to the diskrecorder (source device) 210.

With this third example, this transmission request is performed bychanging the voltage of the first line, e.g., the reserve line of theHDMI cable 350, in the same way as with the case of transmission of thefunction information, compatible transmission format information, andthe like. Also, with this third example, a transmission request for thefunction information and the like can be output from both of thetelevision receiver 250 and the disk recorder 210. With this thirdexample, detailed description will be omitted regarding the portionscorresponding to those in the first example or second example.

The request side (sink device or source device) requests the reply side(source device or sink device) of transmission (start of conditiontransmission) of the function information indicating that the reply sideis an eHDMI-compatible device by changing the voltage of the first line,e.g., the reserve line of the HDMI cable 350. Here, the CPU of therequest side makes up a function information requesting unit.

Next, the reply side monitors the voltage of the reserve line, and atthe time of transmission (start of condition transmission) of thefunction information being requested from the request side, in the casethat it itself is an eHDMI-compatible device, the reply side changes thevoltage of the reserve line of the HDMI cable 350, thereby transmittingthe function information (reply of being capable of conditiontransmission) to the request side. The request side monitors the voltageof the reserve line to obtain the function information transmitted fromthe reply side. In this case, the reply side makes up a voltage changedetecting unit and a function information transmission unit. Also, therequest side makes up a function information obtaining unit.

Next, the request side changes the voltage of the reserve line in apulse shape, thereby transmitting the transmission format informationthat the request side supports to the reply side. The reply sidemonitors the voltage of the reserve line to obtain the transmissionformat information that the request side supports. In this case, therequest side makes up a format information transmission unit, and thereply side makes up a format information obtaining unit.

Next, the reply side changes the voltage of the reserve line in a pulseshape, thereby transmitting the transmission format information that thereply side supports to the request side. The request side monitors thevoltage of the reserve line to obtain the transmission formatinformation that the reply side supports. In this case, the reply sidemakes up a format information transmission unit, and the request sidemakes up a format information obtaining unit.

FIG. 30 illustrates a configuration example of the disk recorder 210 andthe television receiver 250 in the case that the function informationand the compatible transmission format information is transmitted fromthe disk recorder 210 to the television receiver 250, and also thecompatible transmission format information is transmitted from thetelevision receiver 250 to the disk recorder 210. In this FIG. 30, theportions corresponding to those in FIG. 22 are denoted with the samereference numerals, and detailed description thereof will be omitted.

With the television receiver 250, a transmission request for thefunction information is performed by changing the voltage of the firstline, e.g., the reserve line of the HDMI cable 350, thereby eliminatingthe necessity of the connection switch 450 of the television receiver250. The other configurations of the television receiver 250 in thisFIG. 30 are the same as those of the television receiver 250 in FIG. 22.Note that the configuration of the disk recorder 210 in FIG. 30 is thesame as the configuration of the disk recorder 210 in FIG. 22.

FIG. 31 illustrates a voltage control example of the reserve line. FIG.31( a) illustrates the voltage of the HPD line, FIG. 31( b) illustratesthe voltage of the reserve line. The voltage of the HPD line is stillkept high.

In the case of this example, first, the connection switch on the requestside (the connection switch 451 at the time of the television receiver250 being the request side, and the connection switch 418 at the time ofthe disk recorder 210 being the request side) is set to an on state froman off state just for a predetermined period of time, and such as shownin FIG. 31( b), the voltage of the reserve (eHDMMI−) line is changedform low to high. Thus, transmission of the function information (startof condition transmission) indicating that the reply side is aneHDMI-compatible device is requested from the request side to the replyside.

Thereafter, after elapse of the maximum two seconds, the connectionswitch on the reply side (the connection switch 418 at the time of thedisk recorder 210 being the reply side, and the connection switch 451 atthe time of the television receiver 250 being the reply side) is set toan on state from an off state just for a predetermined period of time,and as shown in FIG. 31( b), the voltage of the reserve (eHDMMI+) lineis changed form low to high. Thus, the function information (reply ofbeing transmittable) indicating that the reply side is aneHDMI-compatible device is transmitted from the reply side to therequest side.

Thereafter, for example, since 100 milliseconds elapsed, for example,during 100 milliseconds, the connection switch on the request side issubjected to switching control, and the voltage of the reserve line ischanged from low to high repeatedly according to the transmission formatthat the request side can support. Thus, the information of atransmission format that the request side can support is transmittedfrom the request side to the reply side (declaration of a transmittableformat on the request side).

Also, thereafter, for example, during 100 milliseconds, the connectionswitch on the reply side is subjected to switching control, and thevoltage of the reserve line is changed from low to high repeatedlyaccording to the transmission format that the reply side can support.Thus, the information of a transmission format that the reply side cansupport is transmitted from the reply side to the request side(declaration of a transmittable format on the reply side).

As described above, the function information indicating that the replyside is an eHDMI-compatible device, and the compatible transmissionformat information, transmitted from the reply side, is confirmed at therequest side, and also the compatible transmission format informationtransmitted from the request side is confirmed at the reply side,following which eHDMI transmission is started between the request sideand the reply side.

Now, description will be made regarding a case where a sink deviceincludes multiple HDMI terminals (HDMI ports) (see the televisionreceiver 250 in FIG. 24).

As described above, after transmission of the function information fromthe reply side (reply of being capable of condition transmission), therequest side changes the voltage of the reserve line to transmit thecompatible transmission format information to the reply side.

Therefore, a sink device of multi-input (television receiver 250) cancontrol the transmission timing of the function information (reply ofbeing transmittable) even in the event that transmission of the functioninformation (start of condition transmission) is requested from a sourcedevice at arbitrary timing for each HDMI terminal, andtransmission/reception of the compatible transmission format informationat each HDMI terminal can be executed in accordance with the processingsituation of itself.

Note that, in FIGS. 32( a) through (c), “DDC5V” denotes the voltage ofthe power supply line, “HPD” denotes the voltage of the HPD line, and“Rsv” denotes the voltage of the reserve line. Input 2 in FIG. 32( b)illustrates that the power supply source of a device has been turned on,or connection has been performed, halfway.

The flowchart in FIG. 33 illustrates, in the case that a request isoutput from a sink device, an example of the processing procedure of theCPU (hereafter, referred to as “CPUsi”) of this sink device.

In step ST41, the CPUsi starts the processing, and thereafter, proceedsto processing in step ST42. In this step ST42, the CPUsi determineswhether or not the voltage (DDC5V) of the power supply line is 5V.

When the voltage (DDC5V) of the power supply line is 5V, in step ST43the CPUsi determines whether or not another HDMI input is currentlyperforming a detection operation of the function information, compatibletransmission format information, and the like. At the time of currentlyperforming a detection operation of another input, in step ST44 theCPUsi determines whether or not detection of another input has ended.

At the time of detection of another input having ended, the CPUsiproceeds to processing in step ST45. Note that when another input is notcurrently performing a detection operation, the CPUsi immediatelyproceeds to the processing in step ST45. In this step ST45, the CPUsichanges the voltage of the reserve line from low to high, and requests asource device of transmission of the function information (start ofcondition transmission).

Next, in step ST46, the CPUsi monitors the voltage of the reserve lineto determine whether or not reply has been received from the sourcedevice, i.e., whether or not the function information (reply of beingtransmittable) has been transmitted. When no reply has been received, instep ST47 the CPUsi determines whether or not two seconds have elapsedsince a transmission request was performed in step ST45. In the event oftwo seconds having not elapsed, the CPUsi returns to the processing instep ST46. On the other hand, at the time of two seconds having elapsed,in step ST48 the CPUsi determines that the source device on the partnerside is an eHDMI-incompatible device.

FIG. 34 illustrates a voltage change example of the reserve line in thecase that determination is made that the source device on the partnerside is an eHDMI-incompatible device. Note that FIG. 25( a) illustratesthe voltage (DDC5V) of the power supply line, FIG. 34( b) illustratesthe voltage of the HPD line, and FIG. 34( c) illustrates the voltage ofthe reserve line.

As shown in FIG. 34( c), with the sink device, the voltage of thereserve line has been changed from low to high, and a transmission(start of condition transmission) request for the function informationhas been transmitted to the source device on the partner side. However,as shown in FIG. 34( c), thereafter, even if two seconds have elapsed,the voltage of the reserve line is still high, and there have been noreply from the source device.

Returning to the flowchart in FIG. 33, at the time of reply having beenreceived in step ST46, in step ST49 the CPUsi changes the voltage of thereserve line to transmit the information of a transmission format(application) that the sink device supports to the source device on thepartner side.

Next, in step ST50, the CPUsi monitors the voltage of the reserve line.Subsequently, the CPUsi detects the compatible transmission format ofthe source device on the partner side from voltage change in the reserveline. Subsequently, in step ST51, the CPUsi starts transmission of aneHDMI signal with the source device on the partner side.

With the processing of the flowchart in FIG. 33, at the time of replyfrom the source device having not been received even if two seconds haveelapsed, the CPUsi immediately determines that the source device is aneHDMI-incompatible device. However, as shown in FIG. 35( c), at the timeof reply from the source device having not been received even if twoseconds have elapsed, the CPUsi may execute retry processing wherein thevoltage of the reserve line is changed from low to high several times(only once is shown in FIG. 35( c)) to output a transmission request(condition transmission start request) of the function information tothe source device on the partner side. Thus, in the case that the sourcedevice has had difficulty in reply due to a busy state, a mistake ofimmediately determining that the source device is an eHDMI-incompatibledevice can be avoided.

Note that FIG. 35( a) illustrates the voltage (DDC5V) of the powersupply line, FIG. 35( b) illustrates the voltage of the HPD line, andFIG. 35( c) illustrates the voltage of the reserve line. FIGS. 35( a)and (b) are the same as FIGS. 34( a) and (b).

The flowchart in FIG. 36 illustrates an example of the processingprocedure of the CPUsi of the sink device in the case that a request isoutput from the source device.

In step ST61, the CPUsi starts the processing, and then proceeds toprocessing in step ST62. In this step ST62, the CPUsi determines whetheror not the voltage (DDC5V) of the power supply line is 5V.

When the voltage (DDC5V) of the power supply line is 5V, in step ST63the CPUsi monitors the voltage of the reserve line to detect change oflow to high.

Subsequently, the CPUsi determines that a request of transmission (startof condition transmission) of the function information from the sourceside, and proceeds to processing in step ST64. In this step ST64, theCPUsi determines whether or not another HDMI input is currentlyperforming a detection operation of the function information, thecompatible transmission format information, and the like.

At the time of currently performing a detection operation of anotherinput, in step ST65 the CPUsi determines whether or not two seconds haselapsed since change in voltage of low to high of the reserve line wasdetected in step ST63. At the time of two seconds having not elapsed,the CPUsi returns to the processing in step ST64. At the time of twoseconds having elapsed, in step ST66 the CPUsi gives up transmission ofthe function information (reply of being transmittable). Note that inthe case of intending to execute transmission of the functioninformation (reply of being transmittable), a request for transmission(start of condition transmission) of the function information is outputfrom the sink side again.

When another input is not currently performing a detection operation instep ST64, the CPUsi proceeds to processing in step ST67. In this stepST67, the CPUsi changes the voltage of the reserve line from low to highto transmit the function information (reply of being transmittable) tothe source device. Subsequently, in step ST68, the CPUsi monitors thevoltage of the reserve line to detect the compatible transmission formatof the source device on the partner side from change in voltage of thereserve line.

Next, in step ST69, the CPUsi changes the voltage of the reserve line ina pulse shape to transmit the information of the transmission format(application) that the sink device supports to the source device on thepartner side. Subsequently, in step ST70, the CPUsi startstransmission/reception of an eHDMI signal with the source device on thepartner side.

The flowchart in FIG. 37 illustrates an example of the processingprocedure of the CPUso of the source device in the case of outputting arequest from the source device.

In step ST81, the CPUso starts the processing, and then proceeds toprocessing in step ST82. In this step ST82, the CPUso determines whetheror not the voltage of the reserve line is in a high state. When thevoltage of the reserve line is not high, in step ST83 the CPUsodetermines that the sink device on the partner side is aneHDMI-incompatible device.

When the voltage of the reserve line is high, the CPUso proceeds toprocessing in step ST84. In this step ST84, the CPUso determines whetheror not the voltage of the reserve line is still high. When the voltageof the reserve line is not still high, the CPUso proceeds to processingin step ST85. In this step ST85, the CPUso determines whether or not thevoltage of the reserve line restores to high after a predeterminedperiod of time. When not restoring to high, the CPUso determines thatconnection has been separated. On the other hand, when restoring tohigh, the CPUso determines that a request has occurred from the sinkdevice, and proceeds to processing in step ST104 of the later-describedflowchart in FIG. 38.

When the voltage of the reserve line is still high in step ST84, theCPUso proceeds to processing in step ST88. In this step ST88, the CPUsochanges the voltage of the reserve line from low to high to requesttransmission (start of condition transmission) of the functioninformation.

Next, in step ST89, the CPUso monitors the voltage of the reserve lineto determine whether or not reply has arrived from the sink device,i.e., whether or not the function information (reply of beingtransmittable) has been transmitted. At the time of reply having notbeen transmitted, in step ST90 the CPUso determines whether or not twoseconds have elapsed since transmission was requested in step ST88. Atthe time of two seconds having not elapsed, the CPUso returns to theprocessing in step ST89. On the other hand, at the time of two secondshaving elapsed, in step ST91, the CPUso determines that transmission tothe sink device on the partner side is impossible, and returns to theprocessing start in step ST81.

At the time of reply having arrived in step S89, in step ST92 the CPUsochanges the voltage of the reserve line in a pulse shape to transmit theinformation of the transmission format (application) that the sourcedevice supports to the sink device on the partner side.

Next, in step ST93, the CPUso monitors the voltage of the reserve line.Subsequently, the CPUso detects the compatible transmission format ofthe sink device on the partner side from change in voltage of thereserve line. Subsequently, in step ST94, the CPUso startstransmission/reception of an eHDMI signal with the sink device on thepartner side.

With the processing of the flowchart in FIG. 37, at the time of replyfrom the sink device having not arrived even after elapse of twoseconds, the CPUso immediately determines that transmission isimpossible. However, at the time of reply from the sink device havingnot arrived even after elapse of two seconds, the CPUso may executeretry processing wherein the voltage of the reserve line is changed fromlow to high several times to output a transmission request (conditiontransmission start request) of the function information to the sinkdevice on the partner side. Thus, in the case that the sink device hashad difficulty in reply due to a busy state, a mistake of immediatelydetermining that transmission is impossible can be avoided.

The flowchart in FIG. 38 illustrates an example of the processingprocedure of the CPUso of the source device in the case that a requestis output from the sink device.

In step ST101, the CPUso starts the processing, and then proceeds toprocessing in step ST102. In this step ST102, the CPUso determineswhether or not the voltage of the reserve line is in a high state. Whenthe voltage of the reserve line is not high, in step ST103 the CPUsodetermines that the sink device on the partner side is aneHDMI-incompatible device.

When the voltage of the reserve line is high, the CPUso proceeds toprocessing in step ST104. In this step ST104, the CPUso monitors thevoltage of the reserve line to detect change of low to high. In thiscase, the CPUso detects a transmission request (condition transmissionstart request) of the function information from the sink device.

Next, in step ST105, the CPUso changes the voltage of the reserve linefrom low to high to transmit the function information (reply of beingtransmittable) to the sink device on the partner side. Subsequently, instep ST106, the CPUso monitors the voltage of the reserve line to detectthe compatible transmission format of the sink device on the partnerside from change in voltage of the reserve line.

Next, in step ST107, the CPUso changes the voltage of the reserve linein a pulse shape to transmit the information of the transmission formatthat the source device supports to the sink device on the partner side.Subsequently, in step ST108, the CPUso starts transmission/reception ofan eHDMI signal with the sink device on the partner side.

As described above, with the AV system 200 shown in FIG. 1, the diskrecorder 210 notifies the television receiver 250 of the informationindicating that it itself is an eHDMI-compatible device, and theinformation of the transmission format (application) supported, when thetelevision receiver 250 is connected thereto via the HDMI cable 350, orwhen a transmission request is received from the television receiver250.

On the other hand, for example, as shown in FIG. 39, with an AV system200A wherein an eHDMI-incompatible disk recorder 210A and the televisionreceiver 250 are connected with the HDMI cable 350, the above functioninformation and transmission format information are not notified fromthe disk recorder 210A to the television receiver 250.

Therefore, the television receiver 250 can recognize whether or not thedisk recorder 210 includes communication units (high-speed datainterface, SPDIF reception circuit), i.e., whether or not the diskrecorder 210 is an eHDMI-compatible device, and accordingly, anunnecessary signal can be prevented from being transmitted to the diskrecorder 210A which is an eHDMI-incompatible device via thecommunication path made up of the reserve line and the HPD line.

Also, the television receiver 250 can obtain from the disk recorder 210which is an eHDMI-compatible device the information of the transmissionformat that this disk recorder 210 supports, and accordingly,compatibility with the SPDIF signal and the Ethernet signal of this diskrecorder 210 can be readily known.

Note that, as described in the above embodiment, the functioninformation is notified from the disk recorder 210 which is aneHDMI-compatible device to the television receiver 250, which indicatesthat the disk recorder 210 is an eHDMI-compatible device. Afterrecognizing that the disk recorder 210 is an eHDMI-compatible device,the television receiver 250 can execute transmission of the Ethernetsignal or SPDIF signal via the communication path made up of the reserveline and the HPD line of the HDMI cable 350.

However, there is a case where the disk recorder 210 intentionallydetermines to shut off communication with the communication units(high-speed data line interface 213, SPDIF reception circuit 417). Forexample, this case is a case where the network terminal 225 is connectedto a network, and communication using this network is prioritized, or acase where the power of the CPU 221 is shifted to another process withinthe device, or the like. For example, the CPU 221 determines whether ornot communication by the communication units is thus shut off. Here, theCPU 221 makes up a shutoff determining unit.

When determining to shut off communication by the above communicationunits, the disk recorder 210 transmits communication informationindicating shutoff of communication to the television receiver 250. Forexample, the disk recorder 210 inserts the above communicationinformation during the blanking period of a video signal to betransmitted to the television receiver 250 using the above TMDS channelin the same way as the above function information, thereby transmittingthis communication information to the television receiver 250. Here, thedisk recorder 210 inserts the above communication information during theblanking period of a video signal, for example, using the AVI InfoFramepacket of HDMI, a GCP packet, or the like.

In the case that the disk recorder 210 inserts the communicationinformation during the blanking period of a video signal to betransmitted to the television receiver 250 using the TMD channel asdescribed above, thereby transmitting this communication information tothe television receiver 250, the television receiver 250 extracts theabove communication information from the blanking period of the videosignal received from the disk recorder 210, thereby receiving thiscommunication information.

Also, for example, the disk recorder 210 transmits the abovecommunication information to the television receiver 250 via the CECline 84 which is the control data line of the HDMI cable 350. In thiscase, the television receiver 250 receives the communication informationfrom the disk recorder 210 via the CEC line 84.

The television receiver 250 can recognize that the disk recorder 210 isin a communication shutoff state by receiving the communicationinformation such as described above. Thus, the television receiver 250can prevent transmission of an unnecessary signal to the disk recorder250 wherein communication using the communication units is shut off, viathe above communication path. Note that, as described above, in the casethat the communication information is transmitted from the disk recorder210 to the television receiver 250, the HDMI transmission unit 212 ofthe disk recorder 210 makes up an information transmission unit, and theHDMI reception unit 252 of the television receiver 250 makes up aninformation reception unit.

Note that, with the above description, the communication information istransmitted from the disk recorder 210 to the television receiver 250,thereby enabling shutoff of communication by the communication units ofthe disk recorder 210 to be recognized at the television receiver 250side. However, the disk recorder 210 can notify the television receiver250 that the disk recorder 210 is in a communication shutoff state, bychanging the voltage of the first line, e.g., the reserve line of theHDMI cable 350. In this case, the disk recorder 210 sets the connectionswitch 418 (see FIG. 20) from an off state to an on state to decreasethe voltage of the reserve line.

The television receiver 250 can obtain the communication informationindicating shutoff of communication by the communication units of thedisk recorder 210 by detecting change in voltage of the reserve line. Inthis case, the CPU 271 of the television receiver 250 makes up aninformation obtaining unit. The television receiver 250 can recognize,as described above, that the disk recorder 210 shuts off communicationby the communication units, by detecting the voltage of the reserve lineto obtain the communication information. Thus, the television receiver250 can prevent an unnecessary signal from being transmitted to the diskrecorder 210 in a communication shutoff state via the abovecommunication path.

Note that, with the above embodiment, description has been made assumingthat the interface conforming to the HDMI standard is used as atransmission path for connecting each device, but the present inventionmay be applied to other similar transmission standards. Also, as anexample, the disk recorder has been used as a source device, and thetelevision receiver has been used as a sink device, but the presentinvention may be applied similarly to a case where other transmissiondevice and reception device are used. Also, the above embodiment hasillustrated a case where electronic devices are connected with the HDMIcable, but the present invention may be applied similarly to a casewhere electronic devices are connected wirelessly.

Industrial Applicability

The present invention allows a signal to be transmitted suitably from areception device to a transmission device, and may be applied to an AVsystem or the like wherein a source device and a sink device areconnected via an HDMI cable.

The invention claimed is:
 1. A reception device comprising: a HDMIreception unit configured to receive video signals from an externaldevice in accordance with an HDMI standard via one or more channelsinterconnected to an HDMI terminal; a high-speed data line interfaceconfigured to communicate with said external device via a pair ofdifferential transmission paths interconnected to said HDMI terminal; aprocessor configured to transmit first function information to saidexternal device for notifying said external device that said receptiondevice includes said high-speed data line interface that supportstransmission of at least one of an Ethernet signal and a digital audiosignal, said first function information being transmitted via a controldata line interconnected to said HDMI terminal; the processor beingfurther configured to receive second function information via thecontrol data line from said external device in response to the firstfunction information, said second function information in turnindicating that said external device also includes a respectivehigh-speed data line interface configured to communicate the at leastone of an Ethernet signal and a digital audio signal with saidhigh-speed data line interface of the transmission device via the pairof differential transmission paths interconnected with said HDMIterminal; the processor being further configured to receivecommunication information indicating a communication shutoff state withsaid external device from said external device via the control data lineinterconnected to said HDMI terminal, and wherein the pair ofdifferential transmission paths include a reserve line and an HPD lineinterconnected to the HDMI terminal, and at least one of said pair ofdifferential transmission paths further includes a function forproviding a connection state of said reception device using a DC biaspotential; and a display unit to display an image based on the videosignals.
 2. The reception device according to claim 1, wherein saidfirst function information further includes information indicating atransmission format that the reception device supports.
 3. The receptiondevice according to claim 1, wherein: the processor is furtherconfigured to receive a transmission request for said first functioninformation from said external device; and, the processor transmits saidfirst function information to said external device upon receipt of saidtransmission request.
 4. The reception device according to claim 3,wherein said processor receives the transmission request for said firstfunction information from said external device via the control data lineinterconnected to the HDMI terminal.
 5. A reception method for areception device comprising the steps of: receiving video signals froman external device in accordance with an HDMI standard via one or morechannels interconnected to an HDMI terminal; communicating with saidexternal device via a pair of differential transmission pathsinterconnected to said HDMI terminal; transmitting first functioninformation to said external device for notifying said external devicethat said reception device includes said high-speed data line interfacethat supports transmission of at least one of an Ethernet signal and adigital audio signal, said first function information being transmittedvia a control data line interconnected to said HDMI terminal; receivingsecond function information via the control data line from said externaldevice in response to the first function information, said secondfunction information in turn indicating that said external device alsoincludes a respective high-speed data line interface configured tocommunicate the at least one of an Ethernet signal and a digital audiosignal with said high-speed data line interface of the transmissiondevice via the pair of differential transmission paths interconnectedwith said HDMI terminal; receiving communication information indicatinga communication shutoff state with said external device from saidexternal device via the control data line interconnected to said HDMIterminal, and wherein the pair of differential transmission pathsinclude a reserve line and an HPD line interconnected to the HDMIterminal, and at least one of said pair of differential transmissionpaths further includes a function for providing a connection state ofsaid reception device using a DC bias potential; and displaying an imagebased on the video signals.
 6. A reception device comprising: a videosignal reception unit configured to receive video signals from anexternal device via a transmission path with a plurality of channelsusing a differential signal; a communication unit configured tocommunicate with said external device via a communication path made upof a pair of differential transmission paths included in saidtransmission path; a function information transmission unit configuredto transmit first function information indicating that said receptiondevice includes said communication unit to said external device via acontrol data line making up said transmission path; and a functioninformation reception unit configured to receive second functioninformation which is transmitted from said external device via thecontrol data line, said second function information indicating that saidexternal device includes a communication unit configured to executecommunication via said communication path; the function informationtransmission unit being further configured to receive communicationinformation indicating a communication shutoff state with said externaldevice from said external device via the control data line, and whereinthe pair of differential transmission paths included in saidcommunication path are a reserve line and an HPD line making up an HDMIcable, and at least one of said pair of differential transmission pathsincludes a function for notifying the connection state of said receptiondevice using a DC bias potential; and a display unit to display an imagebased on the video signals.
 7. The reception device according to claim6, wherein the reception device being arranged in operation to monitor avoltage of the reserve line; and if the voltage of the reserve line isin a high state, the function information transmission unit transmitsthe first function information, the function information reception unitreceives second function information.